Patent Publication Number: US-9403056-B2

Title: Multiple degree of freedom rehabilitation system having a smart fluid-based, multi-mode actuator

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national state filing under 35 U.S.C. §371 of International Application PCT/US2010/028121, filed Mar. 22, 2010, entitled A MULTIPLE DEGREE OF FREEDOM REHABILITATION SYSTEM HAVING A SMART FLUID-BASED MULTI-MODE ACTUATOR, and claims the benefit of priority of U.S. Provisional Patent Application No. 61/162,087 filed Mar. 20, 2009, U.S. Provisional Patent Application No. 61/267,193 filed on Dec. 7, 2009, and U.S. Provisional Patent Application No. 61/302,666 filed on Feb. 10, 2010, all of which are incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A rehabilitation system that combines robotics and interactive gaming to facilitate performance of task-specific, repetitive, upper extremity/hand motor tasks, to enable individuals undergoing rehabilitation to improve the performance of coordinated movements of the forearm and hand is disclosed. More specifically, the rehabilitation system includes a two degree-of-freedom (DOF) robotic, upper limb rehabilitation system and interactive gaming hardware that is coupled to a computer, to provide a virtual reality-like environment. 
     2. Summary of the Prior Art 
     Stroke is a major cause of disability in the United States with approximately 800,000 new cases reported annually, of which about 150,000 die. Typically, there are over 4.5 million stroke survivors in the population at any given time. Limited motor recovery in the paretic upper limb accounts for a large share of the disabling sequelae. Indeed, only about a small percentage of stroke sufferers with initial complete upper limb paralysis ever recover functional use of the limb during their lifetime. 
     The physical effects of stroke are variable and may include impairment in motor and sensory systems, language, perception, emotional and cognitive function. Impairment of motor function usually involves paralysis or paresis of the muscles on the side of the body that is contralateral to the side of the brain lesion. Of all impairments that result from stroke, perhaps the most disabling is hemiparesis of the upper limb. 
     Population-based statistics indicate that between 73% and 88% of first-time strokes result in an acute hemiparesis of the upper and/or lower limbs. The upper limbs are of special concern because the impact of upper-extremity impairments on disability, independence, and quality of life is so marked. Consequently, improvement in motor abilities, and, more specifically, functional use of the upper extremity, is considered one of the primary goals in post stroke rehabilitation. However, even with rehabilitation, the functional recovery of arm and hand use is generally limited when compared with that of the lower extremities. 
     Traumatic brain and incomplete spinal cord injuries are other conditions that often leave patients with similar impairments and functional limitations. In both instance, the injury sustained is lifelong. 
     Traumatic Brain Injury (TBI) is a worldwide major public health problem. The Center for Disease Control and Prevention (CDC) estimates that 235,000 Americans are hospitalized annually with TBI and survive. Sadly, approximately 80,000 of these survivors—roughly one-third of the total—are left with long-term disability. An estimated 10,000 or more who sustain TBI, but are not hospitalized, also become disabled each year. 
     Long-term disability after TBI includes problems with motor control, i.e., weakness, spasticity, and instability; cognition, i.e., thinking, memory, and reasoning; sensory processing, i.e., sight, hearing, touch, taste, and smell; communication, i.e., expression and understanding; and behavior or mental health, i.e., depression, anxiety, personality changes, aggression, acting out, and social inappropriateness. The CDC estimates the prevalence of disability resulting from TBI in the U.S. to be 5.3 million. Moreover, the annual direct and indirect costs including those due to work loss and disability have been estimated at $60 billion. The incidence of TBI has been exacerbated by the conflicts in Iraq and Afghanistan where, tragically, TBI has become one of the most prevalent injuries among soldiers. 
     Spinal Cord Injury (SCI) requires on-going, multiple disciplinary efforts to stabilize, diminish or prevent secondary impairments and complications and to improve or maintain social role functioning and quality of life for the individual throughout the remainder of his/her life. There are approximately 250,000 persons with SCI in the United States, and an additional 10,000 sustain SCI injuries annually. The estimated annual national economic impact of SCI is about $9.73 billion. 
     Because the average age at time of an SCI is 32, specialized care is necessarily long-term. Persons with SCI have increasingly longer life expectancies, and as they age they risk developing secondary conditions. Over 50% of people with SCI have cervical injuries resulting in plegia of all four extremities (tetraplegia) leading to impairments in both mobility as well as independence in activities of daily living. Out of all cervical injuries leading to tetraplegia more then 50% are incomplete, resulting in paresis, which is the ability to perform impaired or inefficient movements. 
     Stroke/TBI/SCI survivors historically receive intensive, hands-on physical and occupational therapy to encourage motor recovery. However, due to economic pressures on the U.S. health care system, individuals are receiving less therapy and are being discharged from rehabilitation hospitals and clinics sooner than formerly was the case. 
     Robotic training is a new technology that shows great potential for application in the field of neuro-rehabilitation in either an in-patient or an out-patient setting. Robotic training has several advantages, e.g., adaptability, data collection, motivation, alleviation of patient safety concerns, and the ability to provide intensive individualized repetitive practice. Studies on the use of robotic devices for upper extremity rehabilitation after stroke have shown significant increases in upper limb function, dexterity and fine motor manipulations, as well as improved proximal motor control. 
     However, there are no available training devices that enable flexion/extension movements of the fingers and the hand in conjunction with supination/pronation of the forearm. These movements are synergistic and important to daily functional tasks such as eating, dressing, and grooming. Consequently, a robotic device that facilitates the performance of coordinated forearm pronation/supination movements and trains hand grasp/release movements would be highly desirable because recovery of these movements is a problem in the rehabilitation of individuals post stroke. 
     SUMMARY OF THE INVENTION 
     Although traditional rehabilitation techniques address the need for targeting the recovery of upper extremity motor skills via physical therapy protocols based on a one-to-one interaction between a therapist and a patient, they are limited in providing high intensity, high repetition training. The use of robotics has the potential to provide such training at a cost that is compatible with the financial constraints that mark the health care system in the U.S. and elsewhere in the world and, furthermore, to expand the scope of rehabilitation training. The invention herein described fills a gap in the current offering of robotic systems for rehabilitation. The invention targets coordinated movements of the forearm and of the hand and individual fingers—a key aspect of rehabilitation in several groups of patients who show limited motor ability in the control of the upper extremities. 
     In one embodiment, a two degree-of-freedom robotic interface includes a smart fluid actuator system, which has a first, smart fluid-based, e.g., magneto-rheological fluid (MRF), electro-rheological fluid (ERF), and the like, actuator and a second, smart fluid-based actuator, the two actuators being structured and arranged to operate in either a linear mode or a rotary mode. In both linear and rotary modes, the smart fluid-based actuator is structured and arranged to selectively apply a controllable motive force or a damping force on demand. 
     Each of the actuators is capable of operating in at least one of a pure damping mode, a pure braking mode, a pure actuation mode. Preferably, the first and second smart fluid-based actuators are positioned in-line with respect to each other and/or concentric with one another, the first smart fluid-based actuator providing linear actuation and the second smart fluid-based actuator providing rotary actuation. Alternatively, the first smart fluid-based actuator and the second smart fluid-based actuator are disposed perpendicular to one another; the first smart fluid-based actuator providing linear actuation and the second smart fluid-based actuator providing “rotary” actuation by converting rotary movement into linear translation via a rack-and-pinion device. 
     The addition of an external hydraulic circuit to a smart fluid-based, e.g., ERF, damper allows the actuator to benefit from the controllability and response time of the smart (control) fluid. The close proximity of the main valve of the actuator to the piston provides an improved solution to controlling the hydraulic system. The external hydraulic circuit includes at least one of a pump assembly(ies); a plurality of hydraulic lines that are fluidly coupled between each of the at least one pump assembly(ies) and at least one actuator portion of the robotic interface; and a sensing device(s). 
     Optionally, the hydraulic circuit can also include a manifold. The manifold switches and modulates the flow of smart fluid from the pump assembly, which pumps in a single direction, through the actuator. 
     The controller includes a first processing device and a second processing device that are adapted to inter-communicate. The first processing device can provide a hosting function and is adapted to communicate with and between at least one of the second processing device, a patient/user&#39;s graphical display device, and a third-party graphical display device, which could be used, e.g., for monitoring a patient/user&#39;s performance. The second processing device provides a real-time operating system that is electrically coupled to the robotic interface device to receive data signals therefrom and to transmit control data thereto. 
     The control hardware is connected to a computer or similar gaming console that provides a virtual reality simulation in order to enhance motor learning by engaging patients in the therapeutic exercise via interactive gaming. The simulation presents visuomotor integration tasks to the patient as part of the games or scenes and challenges the patients with cognitive and problem solving tasks embedded in the games. The gaming console can be an optional feature of the system. 
     An optional gaming interface includes at least one input/output device that is structured and arranged to enable a patient/user to interact with software being executed on the gaming interface; and a display device that is adapted to display graphical images that are representative of the patient/user&#39;s manipulation of the robotic interface. 
     Although the multi-mode actuators are component parts of the rehabilitation system, the invention also includes stand-alone multi-mode actuators for general application that can be controlled to produce at least one of a desired motive force and a desired resistive force. The actuator can include a linear, smart fluid-based actuator portion and a rotary, smart fluid-based actuator portion, e.g., a fixed-vane type actuator and a sliding-vane type actuator. Alternatively, the actuator can include a pair of linear, smart fluid-based actuator portions that are disposed perpendicular to each other. 
     Each of the smart fluid-based actuator portions has an integral, smart fluid-based valve. The smart fluid-based valves are disposed within a housing and structured and arranged to provide at least one channel between a first electrode and a second electrode, one of said electrodes going to ground and another of said electrodes being electrically-coupled to the power supply, to activate the smart fluid when current or high voltage are distributed to the electrode that is electrically coupled to the power supply, to increase the yield strength of the smart fluid. Alternatively, the smart fluid-based valves are disposed within a housing and structured and arranged to provide at least one channel between a first electrode and a second electrode, one of said electrodes going to ground and another of said electrodes being electrically-coupled to the power supply, to activate the smart fluid when current or high voltage are distributed to the electrode that is electrically coupled to said power supply, to control a pressure drop across said valves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is pointed out with particularity in the appended claims. The advantages of the invention described above, together with further advantages, may be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily drawn to scale, and like reference numerals refer to the same parts throughout the different views. 
         FIG. 1  shows a two degree-of-freedom robotic hand rehabilitation system according to the invention as claimed; 
         FIG. 2A  shows a diagrammatic view of an in-line, two degree-of-freedom hand rehabilitation interface according to the invention as claimed; 
         FIG. 2B  shows a diagrammatic view of two degree-of-freedom hand rehabilitation interface having linear actuators disposed at 90-degrees from each other according to the invention as claimed; 
         FIG. 3  shows a diagrammatic view of an illustrative maze game that can be run on the gaming engine in accordance with the invention as claimed; 
         FIG. 4A  shows a diagrammatic view of a smart fluid-based linear actuator in accordance with the invention as claimed; 
         FIG. 4B  shows a cross section of the linear actuator shown in  FIG. 4A ; 
         FIG. 5A  shows an isometric diagrammatic view of a smart fluid-based, rotary, sliding-vane actuator in accordance with the invention as claimed; 
         FIG. 5B  shows a plan view of the sliding-vane actuator shown in  FIG. 5A ; 
         FIG. 6A  shows a diagrammatic view of a pump assembly and hydraulic circuit with a manifold in accordance with the invention as claimed; 
         FIG. 6B  shows a diagrammatic view of a pump assembly and hydraulic circuit in accordance with the invention as claimed; 
         FIGS. 7A and 7B  show cross-section views of the sliding-vane actuator shown in  FIGS. 5A and 5B  taken from different elevations; 
         FIG. 8  shows a diagrammatic view of a rotary, fixed-vane actuator in accordance with the invention as claimed; 
         FIG. 9A  shows a diagrammatic view of the inner portion of the fixed-vane actuator shown in  FIG. 8 ; 
         FIG. 9B  shows a diagrammatic view of an alternative inner portion of the fixed-vane actuator shown in  FIG. 8 ; 
         FIGS. 10A and 10B  show cross-section views of the fixed-vane actuator shown in  FIG. 8 ; 
         FIG. 11  shows a diagrammatic view of the internal operation of the fixed-vane actuator shown in  FIG. 8 ; 
         FIG. 12A  shows a diagrammatic view of a rotary vane pump assembly in accordance with the invention as claimed; 
         FIG. 12B  shows an exploded view of the lid assembly of the rotary vane pump assembly shown in  FIG. 12A ; 
         FIGS. 13A and 13B  show isometric views of the pumping mechanism disposed within the rotary vane pump assembly shown in  FIG. 12A ; 
         FIG. 14  shows a detail of the pumping mechanism shown in  FIGS. 13A and 13B  that includes the various operations states of the vanes; 
         FIG. 15  shows a cross-section of a plan view of the rotary vane pump assembly shown in  FIG. 12A ; 
         FIG. 16  shows a detail of a vane for the rotary vane pump assembly shown in  FIG. 12A ; 
         FIG. 17  shows a first diagrammatic view of an optional piezoelectric transducer-based manifold in accordance with the invention as claimed; 
         FIG. 18  shows a second diagrammatic view of an optional piezoelectric transducer-based manifold in accordance with the invention as claimed; 
         FIG. 19  shows a cross-section view of the manifold shown in  FIGS. 17 and 18  that is configured for operation in an actuator mode (forward pumping direction); 
         FIG. 20  shows a cross-section view of the manifold shown in  FIGS. 17 and 18  that is configured for operation in an actuator mode (reverse pumping direction); 
         FIG. 21  shows a cross-section view of the manifold shown in  FIGS. 17 and 18  that is configured for operation in a damper/brake mode (forward pumping direction); 
         FIG. 22  shows a cross-section view of the manifold shown in  FIGS. 17 and 18  that is configured for operation in a damper/brake mode (reverse pumping direction); 
         FIG. 23  shows a cross-section view of the manifold shown in  FIGS. 17 and 18  that is configured for a bypass mode of operation; 
         FIGS. 24A and 24B  shows frameworks of the controlling system for the rehabilitation system in accordance with the invention as claimed; 
         FIG. 25  shows a diagrammatic view of an embodiment of a graphic user interface for the rehabilitation system in accordance with the invention as claimed; 
         FIG. 26  shows a diagrammatic view of the log spiral trajectory of a fingertip pivoting about the MCP joint; 
         FIG. 27  shows a first diagrammatic view of a sweeper-type handle assembly; 
         FIG. 28  shows a second diagrammatic view of a sweeper-type handle assembly; 
         FIG. 29  shows a first diagrammatic view of a four-bar mechanism handle assembly; 
         FIG. 30  shows a second diagrammatic view of a four-bar mechanism handle assembly; 
         FIG. 31  shows a first diagrammatic view of a slider/crank handle assembly; 
         FIG. 32  shows a second diagrammatic view of a slider/crank handle assembly; 
         FIG. 33  shows a diagrammatic view of a “tracking plate” handle assembly; 
         FIG. 34  shows a first diagrammatic (plan) view of a paddle-type handle assembly; 
         FIG. 35  shows a second diagrammatic view of a paddle-type handle assembly; 
         FIG. 36  shows a diagrammatic view of a second embodiment of a paddle-type handle assembly; 
         FIG. 37  shows an embodiment of a two degree-of-freedom hand rehabilitation system with conventional, linear-type motor actuators; 
         FIG. 38A  shows the two degree-of-freedom hand rehabilitation system in  FIG. 37  when the handle assembly is in the fully released position; 
         FIG. 38B  shows the two degree-of-freedom hand rehabilitation system in  FIG. 37  when the handle assembly is in the grasped position; 
         FIG. 39A  shows a diagrammatic view of the linear motor actuator for the rotary degree of freedom; 
         FIG. 39B  shows a detail of the linear motor actuator shown in  FIG. 39A ; 
         FIG. 39C  shows a cross-section of the linear motor actuator shown in  FIG. 39A ; and 
         FIG. 40  shows a control diagram for the spring effect of a conventional actuator. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     The mechatronic, hand rehabilitation system disclosed herein includes hardware and software components, which are described in greater detail below. The performance of the entire hand rehabilitation system depends on the proper selection and matching of components, which include simple mechanical elements such as gears and bearings as well as more advanced devices such as servo drives. The hardware components of the hand rehabilitation system include a multiple, e.g., two, degree-of-freedom (DOF) robotic hand rehabilitation interface; a gaming interface; and a computer-based controller with a data acquisition system. 
     A multiple degree-of-freedom hand rehabilitation system was described in U.S. Provisional Patent Application No. 61/162,087 filed on Mar. 20, 2009, which is incorporated herein in its entirety by reference. Although this disclosure will describe the hand rehabilitation system and the robotic hand rehabilitation interface in terms of only two degrees-of-freedom, those of ordinary skill in the art can appreciate that a more sophisticated system with additional degrees-of-freedom, i.e., greater than two, can be manufactured in accordance with the teachings of this disclosure. 
     Referring to  FIG. 1 , an illustrative embodiment of a multiple DOF robotic hand rehabilitation system  150  is shown. The system  150  shown includes a multiple, e.g., two, DOF robotic interface  151  having a translatable, rotatable, ergonomic handle assembly, a multi-mode actuator system, and at least one sensing device; a multiple-dimension gaming interface  152  that includes a display device  159 , an input/output (I/O) interface, and related software for generating display gaming images; a hydraulic circuit  155 , which includes a pump assembly  153 ; a power supply  154 ; and a controlling system  156 . 
     Multiple DOF Robotic Interface 
     A variable resistance hand rehabilitation device was disclosed in U.S. patent application Ser. No. 12/475,821 filed Jun. 1, 2009, which claims the benefit of U.S. Provisional Patent Application No. 61/130,484 filed on May 30, 2008, which are both incorporated herein in their entirety by reference. An ergonomic handle for a two DOF robotic hand rehabilitation device was disclosed in U.S. Provisional Patent Application No. 61/267,193 filed on Dec. 7, 2009, which is also incorporated herein in its entirety by reference. 
     A two DOF, robotic hand rehabilitation interface  151  having a handle assembly  163  that is adapted to translate along and to rotate about an axis of rotation (AXIS) and that is in operational communication with in-line, concentric linear and rotary actuators  157  and  158  is shown in  FIG. 2A . The interface  151  and, more particularly, the actuators  157  and  158  are adapted to provide resistive active movement in response to patient/user translational motion during grasp/release hand movement and/or to rotational motion in response to supination/pronation movement of the forearm; as well as to provide active forces and/or torques to assist, e.g., to guide, the patient/user&#39;s motions. Each of the linear actuator  157  and the rotary actuator  158  is directly and operatively coupled to the handle assembly  163  via an output shaft  166 . 
     The linear portion, i.e., the grasp/release portion, of the interface  151  extends between the linear actuator  157  disposed at a first, distal end of the interface  151  and the handle assembly  163  disposed at the proximate end of the interface  151 . An output shaft  166  extends along the axis of rotation (AXIS), operatively coupling the handle assembly  163  to the linear actuator  157 . In pertinent part, the output shaft  166  is adapted to pass through openings provided in the housing portion of the linear actuator  157  so that activation of smart (control) fluid flowing into and within the linear actuator  157  can be used to modify the resistive force of the output shaft  166  to translational forces. Although  FIG. 2A  shows two actuators  157  and  158 , those of ordinary skill in the art can appreciate that the design could include a single actuator or more than two actuators. 
     At or near the handle assembly  163  (at the proximate end), the output shaft  166  can be releasably and mechanically attached to a first sensing device, e.g., a load cell  167 , which can, in turn, be releasably and mechanically attached to the translating handle portion  163   a  of the handle assembly  163 . Load cells  167  are well known to the art and will not be discussed in detail. Preferably, the load cell  167  is adapted to provide pressure and/or strain data directly to the controlling system  156 . 
     A second sensing device, e.g., a linear potentiometer  168 , can also be attached to the translating handle  163   a , to measure absolute position of the translating handle  163   a  with respect to the stationary handle  163   b  or another fixed position. Linear potentiometers  168  are well known to the art and will not be discussed in detail. Preferably, the linear potentiometer  168  is adapted to provide displacement data directly to the controlling system  156 . 
     The rotary portion, i.e., the supination/pronation portion, of the interface  151 , extends between the rotary actuator  158  and the handle assembly  163 . The output shaft  166  is adapted to pass through openings provided in the exterior of the rotary actuator  158  so that activation of smart fluid flowing into and within the rotary actuator  158  can modify the resistive force of the output shaft  166 . Hard stops  161   a  and  161   b  can be installed or disposed on one of both of the parallel linear shafts  162 , to adjust maximum and minimum allowable handle stroke in a rotational direction. 
     At or near the distal end, on a distal side of the rotary actuator  158 , a third sensing device, e.g., an extension spring potentiometer  165   a  and its corresponding pulley  165   b , is disposed. The extension spring potentiometer  165   a  is adapted to measure the absolute angle of the handle assembly  163  with respect to the “neutral position” of the interface  151 . Potentiometers  165   a  are well known to the art and will not be discussed in detail. Preferably, the potentiometer  165   a  is adapted to provide rotational velocity and/or rotational displacement data directly to the controlling system  156 . 
     On the opposite, proximate side of the rotary actuator  158 , a fourth sensing device, e.g., a torque cell  169 , can be operatively coupled to the output shaft  166 , e.g., using a rotary actuator adapter (not shown) that is adapted to lock the rotation of the interior vane disposed within the rotary actuator  158  and the output shaft  166  to the torque cell  169 . A helical shaft coupling (not shown) can be used to couple the torque cell  169  to a flexible shaft coupling  171 . The flexible shaft coupling  171  prevents binding of the output shaft  166  by compensating for any non-concentricity. 
     A reaction torque sensor, such as a torque cell  169 , measures torque, i.e., a force associated with the clockwise or counterclockwise rotation of the handle assembly  163  about the axis (AXIS) and, resultingly, the output shaft  166 , directly. Preferably, the torque cell  169  is adapted to provide torque, rotational velocity, and/or rotational displacement data directly to the controlling system  156 . 
     Although the robotic interface  151  has been and will be described hereinafter as having in-line, concentric and coaxial linear and rotary actuators  157  and  158 , alternatively, as shown in  FIG. 2B , the robotic interface  151  can also be designed to employ a pair of linear actuators  157   a  and  157   b  that are structured and arranged in a 90-degree configuration  33 . A first linear actuator  157   a  can be disposed in-line with and coaxial with an output shaft  166   a  for grasp/release motion. A second linear actuator  157   b  can be disposed perpendicular to or normal to the axis of rotation of the output shaft  166   a.    
     With this embodiment, the handle assembly  163  is further mechanically coupled to a gear system, e.g., a precision rack-and-pinion gear system  34 , that is adapted to convert pronation/supination-related rotation of the handle assembly  163  into linear motion of the output shaft  166   b . More specifically, as shown in  FIG. 2B , the gear system  34  converts counterclockwise rotation  36  of the handle assembly  163  into linear displacement  37  of a rack slide  35  in the direction of the output shaft  166   b  of the second linear actuator  157   b . Thus, torque is converted to linear force, which can be measured using, for example, a load cell that is mounted on a rack slide  35 . 
     The handle assembly  163  shown in  FIG. 2A  and  FIG. 2B  restrains the metacarpophalangeal (MCP) joint, requiring the distal interphalangeal (DIP) joint and the proximal interphalangeal (PIP) joint, respectively, the second and third joints on the fingers, to execute a grasping motion. This movement, however, can be very uncomfortable. 
     To address the possible discomfort, an ergonomic handle assembly for inclusion in the hand rehabilitation system has been designed to allow one to achieve a natural finger and finger joint trajectory during grasp/release motions, which is to say using the MCP joint as a pivot and the finger tips following a spiral or log spiral motion rather than a linear motion ( FIG. 26 ). 
     Embodiments of ergonomic handle assemblies are shown in  FIG. 27  and  FIG. 28  (“sweeper” design),  FIG. 29  and  FIG. 30  (four-bar mechanism concept),  FIG. 31  and  FIG. 32  (“slider/crank” concept),  FIG. 33  (“tracking plate” concept), and  FIGS. 34 and 35  (“paddle” concept). After evaluation of each of the concepts in detail, the “paddle” concept was determined to be best at allowing a patient/user to place his/her palm onto an adjustable handle butt  170  while the patient/user&#39;s fingers are attached to a paddle assembly  175  that is structured and arranged to convert the circular, viz. log spiral, motion of the fingers into linear motion. 
     Referring to  FIG. 34  and  FIG. 35 , the handle assembly  180  includes a static handle butt  170 , and a handle block  179 , which are connected by a upper rail  173   a  and a lower rail  173   b . To accommodate hands of different size, the handle butt  170  can be moved linearly along the upper and lower rails  173   a  and  173   b , closer to and further away from the paddle assembly  175 . The diameter or thickness of the handle butt  170  can also be made smaller (for women, children, and persons with smaller hands) or larger (for men and persons with larger hands). 
     An MCP pivot assembly includes an upper MCP pivot mount  172   a  that is translatable and relocatable along and fixedly attachable to the upper rail  173   a  and a lower MCP pivot mount  172   b  that is translatable and relocatable along and fixedly attachable to the lower rail  173   b . Each of the upper and lower MCP pivot mounts  172   a  and  172   b  is rotatably attached to the handle paddle assembly  175 . Bumpstops  174   a  and  174   b  can be disposed on the upper and lower rails  173   a  and  173   b , respectively, to prevent the paddle assembly  175  or sliding links  171   a  and  171   b  from contacting the handle block  179 . 
     The handle paddle assembly  175  can include a top hand plate  175   a  and a bottom hand plate  175   b  that are mechanically coupled by a vertical plate  175   c . A plurality of finger straps  175   d  are stretched between and releasably attached to the top and bottom hand plates  175   a  and  175   b . Links  176   a  and  176   b  operatively couple, respectively, the top hand plate  175   a  to an upper sliding link  171   a  and the bottom hand plate  175   b  to a lower sliding link  171   b . The upper sliding link  171   a  includes an annulus portion that allows the link  171   a  to translate in a linear direction along the upper rail  173   a . The lower sliding link  171   b  includes an annulus portion that allows the link  171   b  to translate in a linear direction along the lower rail  173   b.    
     As a result, in operation, as the joints of the hand apply a non-linear force to the hand straps  175   d , the paddle assembly  175  rotates about the MCP pivot mounts  172   a  and  172   b . With further rotation, the links  176   a  and  176   b  apply a load to the sliding links  171   a  and  171   b , causing linear translation. The sliding links  171   a  and  171   b  can be mechanically connected to an output shaft  166  that is mechanically coupled to one or more linear actuators. 
     A variation to a handle paddle assembly  180  is shown in  FIG. 36  in which the handle butt is offset from the axis of the upper and lower rails so that the axis of the patient/user&#39;s forearm is coaxial to the axis of the rails. For better ergonomics, the center of rotation of the handle butt is structured and arranged to coincide with the MCP joint of the patient/user&#39;s hand. 
     The device can be augmented with the functionality of isolated finger motions by modifying the paddle assembly  175 . For example, to isolate finger motion from grasping motion, the patient/user&#39;s hand should be strapped to the existing main paddle at the proximal phalange, i.e., at the base of the finger, and the distal phalange, i.e., the tip of the finger, should be strapped to an additional subsystem that is hinged to the paddle assembly  175 . The additional subsystem can include a passive elastic element to provide resistance or a compact actuator that can provide assistive forces. All fingers can be strapped to a single subsystem, or a plurality of individual subsystems can be provide for the number of isolated finger motions desired. 
     MRI-Compatible, Smart Fluid-Based, Multi-Mode Actuator 
     The actuator is the principle component that drives the two DOF robotic interface  152  and the two DOF rehabilitation system  150 . Developed technology for stroke/TBI/SCI rehabilitation includes systems that enhance shoulder and wrist movement. However, training devices that are adapted to enable flexion/extension of the fingers and hand, i.e. grasp/release movement, as well as pronation/supination movements, i.e., palm up and palm down movement, of the forearm are virtually unavailable. These movements, however, are synergistic and important to functional tasks such as eating, dressing, and grooming. 
     The prior art suggests the use of some sort of actuator to provide resistive force. Previous implementations of smart fluid-based actuators by others, however, have resulted in single-function brakes and/or dampers. Single-function brakes/dampers are passive devices that are adapted to generate resistance to an applied force but that cannot create a driving force on its own. Accordingly, prior art use of such systems has been limited to discrete applications such as for vibration control, controllable resistance, and motion control. As a result, prior art brakes/dampers may cause problems with patients who cannot move their hands at all. 
     An active force device is one in which the device assists the patient/user to perform a desired movement. Heretofore, when an active force is desirable for a particular application, designers have limited themselves to one of two options. A first option employs a motor with a closed-loop controller. The first option is widely used to reach high force/torque levels. However, disadvantageously, large motors must be used, which are expensive and bulky and, therefore, undesirable. 
     A second option employs a driver in combination with a damper. Disadvantageously, the second option is a more complex, combining two mechatronic systems that must be controlled closely for the system to operate transparently. 
     Notwithstanding, it is possible to provide passive and active, i.e., assistive, force with conventional actuators using, for example, voice coils and hydraulic cylinders. Indeed, the use of a smart fluid-based actuator has several superior features over its counterparts. For example, first, it has high-force density, which is to say, that it can provide forces up to 500 N in a compact design. Second, the relatively high response rate to varying electric fields enables smooth control of forces during rehabilitation games. Finally, smart fluid-based actuators are MRI-compatible, so devices that use them have the option of being made MRI-compatible. 
     In one embodiment, the actuator is adapted to use smart (control) fluids such an electro-rheological fluid (ERF), a magneto-rheological fluid (MRF), and the like, to provide damping/braking selectively. An ERF-based actuator performs exceptionally compared to standard hydraulic system due to the proximity of its control (main) valve to the actuator itself and will be described further herein. 
     An MRI-compatible, smart fluid-based, multi-mode actuator is described in U.S. Provisional Patent Application No. 61/302,666 filed on Feb. 10, 2010, which is incorporated herein in its entirety by reference. 
     A smart (control) fluid-based, multi-mode actuator that is structured and arranged to provide a linear and a rotary actuator mode of operation and/or a damper/brake mode of operation will now be described. In either its linear or its rotary forms, the actuator is adapted to apply either a controllable motive force and/or a controllable damping force. 
     More particularly, the control (main) valve of an ERF-based actuator can be disposed within the actuator itself and, further, can be controlled by varying the strength of an electric field across the main valve. A change in electric field strength at the main valve changes the yield stress of the ERF fluid therein, which affects the pressure drop across the main valve. Hence, pressure and pressure differentials, which affect velocity, can be controlled by controlling the yield stress of the ERF. Since the main valve is disposed inside the actuator itself proximate to the piston (or to a rotary vane member) and, moreover, because ERF reacts, i.e., can be activated by an electric field, on the order of milliseconds, rapid and precise force control is possible. 
     Extensive research has been conducted by others on smart fluid dampers and damper applications. However, the primary focus of others has been on use of dampers as vibration damping elements. Smart fluid actuators, however, have many features that are suitable and desirable for patient rehabilitation applications. For example, they exhibit a high response rate to varying electric (or magnetic) field strength and, moreover, are compatibility with magnetic resonance imaging (MRI). 
     Various actuator types for the multi-mode actuator rehabilitation system will now be described. Use of the generic term “actuator” hereinafter will include use of the same device for damping and braking operations. Hence, the “damper” or “brake” terms will not be included in the description of the device, although, those skilled in the art can appreciate that, by convention, an actuator qua actuator does not perform damping or braking. 
     Smart Fluid-Based, Linear Actuator 
     Referring to  FIG. 4A  and  FIG. 4B , an illustrative embodiment of a smart fluid-based, linear actuator  10  is shown. The smart fluid-based linear actuator  10  draws its principle functionality from a smart (control) fluid such as ERF, MRF, and the like. Although the invention is described including ERF-based actuators, those skilled in the art can appreciate that MRF-based actuators and other high performance actuators are equally suitable for use in this system. 
     The actuator  10  includes a central portion  15  that is mechanically coupled to a first (front) end cap  17  and a second (rear) end cap  16 , to define a plenum or cavity therein. The central portion  15  is structured and arranged to house, inter alia, a piston chamber  26  and  27  and a field-inducing device  30  within the plenum space or cavity. 
     Primary and secondary piston shafts  14  and  13  are disposed through openings  18 , respectively, in the front and rear end caps  17  and  16 . Low-friction bearings  19  are provided in each opening  18  for the purpose of centering the piston shafts  14  and  13  while also permitting the piston shafts  14  and  13  to translate in an axial direction and/or to rotate freely about the translation axis, in a clockwise or a counterclockwise direction, without unwanted side loads or friction. 
     The piston chamber  26  and  27  is structured and arranged to accommodate a piston  20  and a volume of smart fluid. The piston  20  divides the plenum or cavity into a first chamber portion  26  and a second chamber portion  27 . The piston  20  is machined to a close tolerance to provide a negligible radial gap, e.g., within one-thousandth of an inch (0.001 in.), between the outer periphery of the piston  20  and the inner surface of the piston chamber  26  and  27 . Maintenance of a negligible radial gap eliminates the need for a piston seal, which can be a major source of friction. 
     The piston  20  translates in a longitudinal direction in response to a force applied to the primary or secondary piston shaft  14  or  13 . A translational force on one side of the piston  20  or the other, i.e., within the first chamber portion  26  or the second chamber portion  27 , can produce a pressure differential between the two chamber portions  26  and  27 . Depending on the location of the pressure differential with respect to the piston  20 , smart fluid flows into/out of the first chamber portion  26  via a conduit  29  and a first input/output port  12  that is integrated into the front end cap  17  and smart fluid flows into/out of the second chamber portion  27  via a conduit  29  and a second input/output port  11  that is integrated into the rear end cap  16 . 
     The piston  20  is mechanically coupled to primary and secondary piston shafts  14  and  13  that are disposed on opposing sides of the piston  20 . The primary piston shaft  14 , typically, has a force or torque applied to it by the patient/user while the secondary piston shaft  13  acts as a volume compensator and/or can be used as an auxiliary connection point, e.g., to a linear potentiometer to measure relative position. 
     Sealing devices, e.g., an O-ring  24  and a low-friction spring seal  25 , are provided to prevent smart fluid from escaping the chamber portions  26  or  27  during movement of the piston  20 . 
     For ERF-based actuators  10 , the field-inducing device  30  can include outer  21 , middle  22 , and bore electrodes  23 , which combination produces the “main valve” or “control valve” of the actuator  10 . The electrodes  21 ,  22 , and  23  are relatively thin, hollow cylinders that are disposed coaxial and concentric about the axis of translation as well as each other. The outer electrode  21  and the bore electrode  23  are electrically coupled to ground while the middle electrode  22  is electrically coupled to a current power source  154 . 
     Concentric, annular gaps  28  are provided between the outer electrode  21  and the middle electrode  22  and between the middle electrode  22  and in the bore electrode  23 . During operation, smart fluid flows through the gaps  28 . However, during an actuator mode of operation, there is no field induced in the smart fluid. During a damper/brake mode of operation, the electrodes  21 ,  22 , and  23  are adapted so that as high voltage is applied to the middle electrode  22 , an electric field of a controllable strength is induced in the smart fluid flowing in the gaps  28 . The induced electric field activates the smart fluid, which is to say causes the yield stress of the smart fluid and, therefore, the resistance to flow to increase. Increased resistance provides the damping/braking. 
     For example, when the handle assembly  163  is subject to a grasp force, the patient/user moves (pulls) the translating handle  163   a  towards the stationary handle  163   b . As the piston  20  is pulled in the direction of the primary piston shaft  14 , the volume of the first piston chamber  26  decreases; hence, smart fluid is forced out of the first chamber portion  26  and through annular gaps  28  between the electrodes  21 ,  22 , and  23  into the hydraulic circuit  155  via the conduit  29  and the first input/output port  12 . At the other end, the volume of the second piston chamber  27  increases. As a result, smart fluid is introduced into the second chamber portion  27  and the annular gaps  28  from the hydraulic circuit  155  via the second input/output port  11  and the conduit  29 . The pressure differential between the first and second piston chambers  26  and  27  determines the degree of resistance to the patient/user&#39;s grasp motion. By activating the smart fluid in the gaps  28  of the field-inducing device  30 , the pressure drop can be controlled to provide more or less resistance. 
     Similarly, when the handle assembly  163  is subject to an active, release force, the patient/user&#39;s hand must resist the force of the translating handle  163   a  as it is forced away from the stationary handle  163   b . Release motion pushes the piston  20  in the direction of the second piston chamber  27  and the secondary piston shaft  13 . As the volume of the second piston chamber  27  decreases, smart fluid is forced out of the second chamber portion  27  and from between the annular gaps  28  between the electrodes  21 ,  22 , and  23  into the hydraulic circuit  155  via the conduit  29  and the second input/output port  11 . At the other end, the volume of the first piston chamber  26  increases so smart fluid is introduced into the first chamber portion  27  and the channel gaps  28  from the hydraulic circuit  155  via the first input/output port  12  and the conduit  29 . Here again, the pressure differential between the first and second piston chambers  26  and  27  determines the degree of resistance to the patient/user&#39;s release motion. 
     During either grasp/release operation, smart fluid flows through the “main valve”  30 , which modulates pressure drop across its length as a function of the electric field strength. Hence, pressure drop, which equates to handle assembly resistance, can be controlled merely by varying the electric field strength. Because smart fluids inherently respond to an increase in electric field strength (or an increase in magnetic field strength), the yield stress of the control fluid increases with increasing field strength and decreases with decreasing field strength. As a result, when a smart fluid is influenced by an electric field (or by a magnetic field), generated by the field-inducing device  30 , the fluid&#39;s yield stress increases, making it more resistive to motion as the thickened fluid flows through the “main valve”  30 . 
     Fluid resistance in the “main valve”  30  can be harnessed mechanically using various configurations of pistons (linear) or vanes (rotary), which are discussed in greater detail below. Advantageously, in an ERF form, an actuator  10  could be made to be fully compatible with magnetic resonance imaging (MRI), which is to say, to be selectively operable in either active or damping modes in high magnetic field environments such as magnetic resonance imaging (MRI). 
     An optional load cell  167 , e.g., a strain gauge, can be mechanically coupled to the primary or secondary piston shaft  14  or  13  to measure load/or and load rate. Strain gauges and their application are well known to the art and will not be discussed in greater detail. Load cells  167  can also be adapted to provide strain data as output to the controller  156 , e.g., wirelessly or via a hardwire coupling (not shown). 
     Smart Fluid-Based, Sliding-Vane, Rotary Actuator 
     Diagrammatic views of an exemplary rotary, sliding-vane actuator (the “Rotary Actuator”)  50  are shown in  FIG. 5A  (isometric) and  FIG. 5B  (plan). The rotary actuator  50  includes a lid assembly  51 , a base assembly  52 , a vane chamber  53 , and a rotary shaft  55 . The rotary actuator  50  also includes a first pair of input/output valves  54   a  and  54   b  on a first side (Side A) and a second pair of input/output valves  56   a  and  56   b  on a second side (Side B)  59 . 
     The two sides  58  and  59  are symmetrical, each providing its own flow path. The function of Side A and Side B will be discussed in greater detail below. Referring to  FIG. 6A  and  FIG. 6B , whereas a linear actuator  10  has two hydraulic lines  41   a  and  41   b  that are fluidly coupled, respectively, to the front valve  12  and the rear valve  11  of the linear actuator  10 , a rotary actuator  50  can have two  41   a  and  41   b  or four hydraulic lines  41   a - 41   d  to opposing sides of the rotary actuator  50 . The number of hydraulic lines  41  determines whether the rotary actuator  50  is “balanced” (2 lines) or “unbalanced” (4 lines). The manifold  130  shown in  FIG. 6A  is optional and will be discussed in greater detail below. 
       FIG. 7A  and  FIG. 7B  show cross-sectional views of the rotary actuator  50  at different elevations for the purpose of showing the function thereof. The rotary actuator  50  includes a circular or substantially circular, rotary, sliding-vane mechanism  60  that is mechanically coupled to the rotary shaft  55  such that rotation of the sliding-vane mechanism  60  produces rotation in the rotary shaft  55 . 
     The circular or substantially circular rotary mechanism  60  is disposed in a non-circular chamber  68 . The rotary mechanism  60  includes a plurality of radial vanes  61  that are biased, e.g., spring-biased, so that the distal edge of each vane  61  remains in contact with the peripheral surface of the chamber  68  during rotation, to provide a seal. 
     The vanes  61  operate in one of three modes: a fully extended mode  61   a , a fully depressed mode  61   b , and a partially-depressed (or partially-extended) mode  61   c . As shown in  FIG. 7 , there is space  65  for control fluid between adjacent vanes  61  that are both fully extended  61   a ; between one vane that is fully extended  61   a  and an adjacent vane that is partially-extended  61   c ; between adjacent vanes that are both partially-extended  61   c ; and between adjacent vanes that are fully depressed  61   b  and partially-extended  61   c . In other words, there is no or substantially no space for control fluid between adjacent vanes  61  that are both fully depressed  61   b.    
     The rotary actuator  50  also includes plural electrodes  63  that are separated by a fluid gap  70 . One electrode is coupled to ground and the other is coupled to a power source (not shown). The power source is adapted to provide current or high voltage to influence the ERF or the MRF, respectively. The electrodes  63  and fluid gap  70  provide a “main valve”  62  (for Side A  58 ) and a “main valve”  64  (for Side B  59 ), for controlling pressure drops. Indeed, by adjusting high-voltage delivered to the electrodes  63  and, thereby, the strength of the electric field induced in the control fluid in the gaps  70 , the pressure drop and pressure differential (on either side of the main valve  62 ) can be varied. 
     Referring to  FIG. 7B , internal flow pathways  69   a  and  69   b  for Side A  58  and Side B  59 , respectively, provide fluid communication between the Side A input/output  54   a , the Side A valve  62 , and the Side A input/output  54   b ; and between the Side B input/output  56   a , the Side B valve  64 , and the Side B input/output  56   b , respectively. In this balanced design, there are two independent flow pathways  67   a  and  67   b  with little internal fluid exchange between the two. The direction of the flow can be clockwise or counterclockwise. 
     Each “side” of the rotary actuator  50  cycles smart control fluid through the internal flow pathways  67   a  and  67   b  and external hydraulic circuit  155  and through the gaps  70  in the “main valves”  62  and  64 . The distribution of flow is controlled by the pressure difference between the “main valve”  62  or  64  and the external hydraulic circuit  155 . 
     In the Side A internal flow pathway  67   a , a volume of control fluid from the hydraulic circuit  155  and/or from the gap  70  enters a sub-chamber  65  of the chamber  68  via the internal flow passageway  69   a , between a first, fully depressed vane  61   b  and an adjacent partially-extended vane  61   c . As the rotary sliding vane device  60  rotates about the axis of the rotary shaft  55 , the biasing spring (not shown) forces the distal end of each vane  61  against the peripheral wall of the chamber  68 . As this happens the volume of the sub-chamber  65  increases to a maximum (while the volume of the fluid remains unchanged or substantially unchanged) and then decreases until the control fluid is output at to the internal flow pathways  71   a.    
     The fluid then passes through the “main valve”  62  and/or is output into hydraulic circuit  155 . As the fluid passes through the main valve  62 , the strength of the field (electric or magnetic) will cause the yield stress of the fluid to increase or decrease accordingly. As the yield stress increases, it becomes more resistive and slows down (dampens or brakes) the action of the rotary shaft  55 . The resistivity can be increased so as to arrest (brake) any movement of the shaft  55 . As the yield stress decreases, it becomes less resistive and speeds up the action of the rotary shaft  55 . 
     Instead of valves, a compressible closed cell foam or the like can be incorporated behind the vanes. These serve dual function; to assist in sealing the vanes during low speed operation by adding a spring behind the system and to take up the volume behind the vanes when they are compressed down. 
     Smart Fluid-Based, Fixed-Vane, Rotary Actuator 
     As an alternative to the sliding-vane actuator  50  described hereinabove, a rotary, fixed-vane actuator (“Fixed-vane Actuator”) can be used. An exemplary fixed-vane actuator  80  is shown in  FIGS. 8-11 . The fixed-vane actuator  80  is adapted to house within an inner plenum or cavity a rotating member  89  to which an output shaft  85  and a single, fixed vane  88  are mechanically attached. 
     The housing elements include a cylindrical case portion  82  and a lid portion  81 . Input/output barbs  83  and  84  are provided in the case portion  82  for fluidly coupling the fluid chamber  79  of the fixed-vane actuator  80 , which is disposed in the inner plenum or cavity, to the hydraulic circuitry  155 . The lid portion is structured and arranged to include a centrally-located opening that accommodates the output shaft  85  as well as a low-friction sealing device  86   c  and a first, upper, low-friction bearing  86   b . The bearing  86   b  is adapted to center the output shaft  85  with a minimal amount of lateral loading. The sealing device  86   c  is provided around the output shaft  85 , to prevent leakage of smart fluid during operation. A removable bearing lid  86   a  is provided to confine the bearing  86   b  and seal  86   c  within the lid portion  81 . 
     As shown in  FIGS. 9A, 9B, 10A, and 10B , a bi-directionally-rotatable rotating member  89  is housed within the inner plenum or cavity provided by the cylindrical case portion  82 . A second, lower, low-friction bearing  86   d  is provided in the base of the case portion  82 , to center the output shaft  85  with a minimal amount of lateral loading. The fixed vane  88  is integrated into or mechanically attached to the outer periphery of the rotating member  89 . 
     The fixed vane  88  is fabricated to provide minimal, friction-less or virtually friction-less clearance between the fixed vane&#39;s outermost radial surface and the inner peripheral wall of the plenum or cavity, to again minimize leakage and/or pressure loss about the fixed vane  88 . The annular region between the outer periphery of the rotating member  89  and the inner surface of the plenum or cavity of the case portion  82  defines a fluid chamber  79 . 
     As the vane  88  rotates, smart (control) fluid passes through the main valve  74  and the hydraulic circuit  155 . The difference in pressures between the front  88   a  and the back  88   b  of the vane  88  will determine the direction and velocity of flow as well as the device&#39;s functionality. During clockwise operation (as shown in  FIG. 11 ), pressurized ERF passes into the fluid chamber  79  through one of the opening  73   a , forcing the fixed vane  88  to rotate in the direction of the arrow. 
     A pressure plate  87   a  and biasing means, e.g., a plurality of biasing springs  87   b , are provided to seal the rotating member  89  within the fluid chamber  79 , to prevent leakage of smart fluid therefrom. The pressure plate  87   a  can be made from or coated with a low-friction material, to minimize friction loss due to contact between the rotating member  89  and the plate  87   a . The springs  87   b  apply a constant or substantially constant force that balances design needs for low friction with needs for low leakage. 
     The fluid chamber  79  is structured and arranged to provide a main valve  74  and plural, e.g., two, sub-chambers  79   a  and  79   b , whose volume is constantly changing as the rotary member  89  and the fixed vane  88  rotate. When operated as an actuator, a pressure difference in the smart fluid between the two sub-chamber sides  79   a  and  79   b  is modulated and promoted by the main valve  74 . The pressure difference gives rise to an output torque in the direction of the lower pressure. Alternatively, when operated as a damper/brake, the fixed vane  88  forces smart fluid though the main valve  74 , which modulates the pressure difference. This is felt on the shaft  85  as a resistance to rotation. 
     A first sub-chamber  79   a  is fluidly coupled to the hydraulic circuitry  155  via a first opening  73   a  in the case portion  82  and in one of the input/output barbs  83  or  84 . A second sub-chamber  79   b  is fluidly coupled to the hydraulic circuitry  155  via a second opening  73   b  in the case portion  82  and in one of the input/output barbs  83  or  84 . The main valve  74  is disposed between and proximate or adjacent to the pair of openings  73   a  and  73   b.    
     As shown in  FIG. 9A , the main valve  74  includes a pair of fluid channels  78 , respectively, which are disposed between a bore electrode  75  and a middle electrode  76  and between the middle electrode  76  and an outer electrode  77 . The bore and outer electrodes  75  and  77  are electrically grounded while the middle electrode  76  is electrically coupled to a current power source. As shown in  FIG. 9B , the main valve  74  includes a plurality, e.g., six, of fluid channels  78 , respectively, which are disposed between a bore electrode  75  and a middle electrode  76 , between a middle electrode  76  and an inner ground electrode  178 , and between the middle electrode  76  and an outer electrode  77 . Insulators  72  for electrically insulating the non-grounded middle electrodes  76 , e.g., plastic inserts, are provided. The bore  75 , inner ground  178 , and outer electrodes  77  are electrically grounded while each middle electrode  76  is electrically coupled to a current power source. 
     To dampen or arrest the rotational velocity of the fixed vane  88 , current is supplied to the middle electrode  76  to activate the smart control fluid within the fluid channels  78  of the valve  74 . As the smart fluid is activated, resistance to flow within the fluid channels  78  and, consequently, the fluid chamber  79  increases, retarding or dampening further rotation. 
     Optionally, pressure sensors (not shown) can be incorporated into the fixed-vane actuator  80  or on either side of the valve  74 , to assist in controlling the device using pressure difference readings directly. 
     Conventional Actuators 
     Heretofore, the invention has been described assuming the use of smart fluid-based actuators. However, the invention can also be practiced using conventional, linear-type motor actuators. Referring to  FIG. 37-39 , there are shown various views and details of a system  190  having a first actuator for the first degree-of-freedom (linear), which includes a linear drive motor  191  and a compliant force sensor  199 , and a second actuator for the second degree-of-freedom (rotary), which includes a linear drive motor  195  and a compliant force sensor  192 . Also shown are a two DOF handle assembly  193  that is mechanically coupled to a linear actuation shaft  194 , a controller  198 , and a pair of motor amplifiers  197   a  and  197   b , which are operatively coupled to a corresponding linear drive motors  191  and  195 . A rack-and-pinion device  196  is provided for converting the rotary motion of the handle assembly  193  into a linear DOF motion of the linear motor  195 . 
     For example,  FIG. 38A  shows a handle assembly  193  that is in the fully-released position, which is to say that the patient/user&#39;s hand is fully opened. As shown, when fully-released, the sliding locks  171   a  and  171   b  move in the direction of the arrow  200   a , causing the shaft  194  to force the force sensor  199  in the same direction  200   b .  FIG. 38B  shows a handle assembly  193  that is in the fully-grasped position, which is to say that the hand is fully or substantially closed. In contrast with the fully-released position, the sliding locks  171   a  and  171   b  move in the direction of the arrow  200   a , causing the shaft  194  to pull the force sensor  199  in the same direction  200   b.    
     As mentioned above, a linear drive actuator with a rack-and-pinion device  196  is provided to convert rotary motion of the handle assembly  193  into a linear motion. Referring to  FIGS. 39A, 39B, and 39C , the linear actuator for the rotary degree-of-freedom, includes a base portion having a guide rail  205  onto which a plurality of guide blocks  208  can be slidably affixed. The guide blocks  208  provide a rigid, low-friction platform for mounting the sensor stages  201  and  202 . Each sensor stage  201  and  202  is independently adjustable on the guide blocks  208  and the guide rail  205  to facilitate aligning the rack-and-pinion device  196  with the linear motor coil/magnet  195 . 
     For example, a first end  201   a  of the outer sensor stage  201  is fixedly attached to a first guide block  208   a , an inner sensor stage  202  is fixedly attached to a second and to a third guide blocks  208   b  and  208   c , and a second end  201   b  of the outer sensor stage  201  is fixedly attached to a fourth guide block  208   d . The outer sensor stage  201  is mechanically coupled to the linear motor  195  so that any force applied by the linear motor  195  results in displacement of the outer sensor stage  201 . 
     The force sensor  192  includes a first spring  206   a  that is disposed about a removable rod  209 , between the first end  201   a  of the outer sensor stage  201  and the inner sensor stage  202  and a second spring  206   b  that also is disposed about a removably rod  209 , between the inner sensor stage  202  and the second end  201   b  of the outer sensor stage  201 . A spring-loaded adjustment screw  207  is provided on at least one end of one of the outer sensor stage  201 . In  FIG. 39C , spring-loaded adjustment screws  207   a  and  207   b  are provided on the first  201   a  and second ends  201   b  of the outer sensor stage  201 , respectively. The spring-loaded adjustment screw  207  ensures that each of the springs  206   a  and  206   b  is compressed a pre-determined distance that is designed to exceed, under any loading condition, the displacement (x) of the inner sensor stage  202 . By displacing springs  206   a  and  206   b  of a known spring constant (k), the force (F) can be determined accurately by measuring the relative displacement (x) between the outer and inner sensor stages  201  and  202  and by using Hooke&#39;s Law, viz. F=k*x. 
     For measuring displacement between the second end  201   b  of the outer sensor stage  201  and the inner sensor stage  202 , a first sensing device  204   a , e.g., linear potentiometer, is fixedly attached to each of the second end  201   b  and the inner sensor stage  202 . The rack portion  196   a  of the rack-and-pinion device  196  is also fixedly attached to an inner sensor stage  202 . As a result, any torque applied to the actuator shaft  194  will cause the rack portion  196   a  and the inner sensor stage  202  to which it is attached to translate in a linear direction depending on whether the pinion portion  196   b  is rotated clockwise or counterclockwise. 
     Translation of the inner sensor stage  202  along the guide rail  205  in response to the torque places further compresses either the first or the second spring  206   a  or  206   b . The linear potentiometer  201   b  measures the displacement associated with the compression or that associated with the tension, which should be equal in a linearly elastic system. Knowing the spring constant (k) and the displacement (x), a force (F) can be calculated using Hooke&#39;s law. 
     When resistive force is purposely added to the linear motor  195 , absent an equal and opposite force, the applied resistive force can cause the outer sensor stage  201  to displace along the guide rail  205 . Accordingly, in order to measure the absolute position of the inner sensor stage  202 , which can be used to determine the handle assembly angle (for a rotary actuator) or the grip position (for a linear system), a relative position measurement between the first end  201   a  and the case of the linear motor  195  using a second sensing device  204   b , i.e., a second linear potentiometer, is needed. The second sensing device  204   b  can be fixedly attached between the first end  201   a  of the outer stage  201  and to the case of the linear motor  195 , which should remain stationary or fixed. Adding any displacement measured by the second sensing device  204   b , which provides a measurement of the motor coil  203  position, to the displacement between the inner sensor stage  202  and the second end  201   b , provides absolute position. 
     Robotic interfaces can also include an actuator selected from the group consisting of ball-screw linear actuators, pneumatic actuators, standard hydraulic actuators, geared rotary DC motors, and geared linear DC motors. 
     Gaming Interface 
     The adaptation of a three-dimensional gaming interface or engine  152  to a rehabilitation system  150  and its advantages are disclosed and described in greater detail in International Patent Application Number PCT/US2010/021483 filed on Jan. 20, 2010, which claims the benefit of U.S. Provisional Patent Application No. 61/145,825 filed on Jan. 20, 2009 and of U.S. Provisional Patent Application No. 61/266,543, filed Dec. 4, 2009—all three of which are incorporated in their entirety herein by reference. As a result, the gaming interface  152  function will not be described in great detail except to describe how the gaming interface  152  interacts with the other components of the system  150 . 
     A game engine is a software system that is designed for the creation and development of video games. For example, an open source 3D game engine, e.g., Panda3D, can be used in the development of the computer graphics for the rehabilitation system. 
       FIG. 3  shows an illustration of an exemplary displayed gaming image  164  that is representative of one of a multiplicity of games or game themes (“scenes”) that can be created by a gaming engine and executed (run) by the gaming interface  152  using input data from the 2 DOF robotic interface  151 , to drive an icon, cursor, or other figure (“dot”  177 ) graphically on the screen of the display device  159 . The illustrative display  164  is a two-dimensional maze, to which a first DOF of the robotic interface  151  is coupled to a first dimension and a second DOF is coupled to a second dimension. Maze games fall into the category of navigation games, to which can be added pick-and-place games, e.g., chess, checkers, and the like, virtual task games, e.g., turning a virtual doorknob, inserting a virtual key in a lock, flicking on or off a virtual light switch, and so forth, obstacle navigation games in which the patient/user avoids virtual objects, and triggered event games in which a virtual scene forces the patient/user to react to an event being displayed. These games can be computer controlled and can use artificial intelligence to react to patient/user input and induced patient/user reactions. 
     The graphical patient interface, i.e., the display device  159  with a displayed, interactive game scene, provides a visual, interactive gaming environment for performing therapeutic exercises using the robotic interface  151 . The interface provides motivation to the patient/user and real-time feedback, e.g., to the patient/user, a practitioner, a therapist, and the like, concerning the quality of the movements performed by the patient/user, to achieve the motor tasks required to play the games. With such an interface, the patient/user is more motivated to perform visuomotor tasks that are part of the rehabilitation session in the most appropriate and useful way to achieve motor recovery. Moreover, the practitioner, the therapist, and the like can monitor each patient/user&#39;s performance and progress to evaluate his/her current state and to design future goals for him/her. 
     Because the extent and nature of the disability may differ from patient to patient, some patients may have problems with grasp and release movements, while others may have problems with supination and pronation. For this reason, a maze design can be created (or selected from existing designs), that allows practitioners, therapists, and the like to focus the therapy on the desired movements of the patient/user&#39;s hand. 
     With two degrees-of-freedom there are several possibilities for virtual reality scenes. A first possible design is to use a first degree-of-freedom to control the x position and a second degree-of-freedom to control the y position in a Cartesian coordinate system. For example, a grasp/release action can result in, i.e., display, movement in a vertical or y-direction, while pronation/supination motion can result in, i.e., display, movement in a horizontal or x-direction, or vice versa. 
     A second possible design uses a first degree-of-freedom to control the direction of the dot  177  and the other degree-of-freedom to control velocity of the dot  177 . An example of this design would be to use the supination/pronation degree-of-freedom for direction control and the grasp/release degree-of-freedom for velocity. 
     A third design is not to use either degree-of-freedom for position, direction, or velocity but instead use them to control another aspect of the virtual reality scene. For example, turning a doorknob, moving a checker or a chess piece, inserting a key in a lock, and so forth. In general, the user-controlled position can be directly or indirectly specified. For the direct method, each position of the handle assembly  163  corresponds to a specific position on the screen of the display device  152 . When the patient/user moves the handle assembly  163 , the represented position follows movement of the handle assembly  163  exactly. For the indirect method, there is an equation of thrust or something similar that drives the represented position. 
     The representative dot  177  can also be given a mass so that a corresponding friction, inertia, etc. can calculated and added, and the position changes accordingly. The patient/user controls the level and direction of thrust with the handle assembly  163 . Force feedback controls the feel of the handles. Either of these methods can be applied to one or both of the degree-of-freedom of the device. 
     With each game, discrete movements of hand grasp/release and forearm pronation/supination can be pre-programmed to control certain aspects of a game, such as navigating the dot through a virtual, multiple-dimensional environment. Advantageously, the virtual environment provides challenges, requires the performance of visuomotor integration tasks (hand-eye coordination), offers real-time visual feedback, and provides input to the controller  156  so that haptic feedback can also be provided. 
     A game or a “scene” from a game can be provided in which certain virtual events, e.g., a collision with a surface or an object and so forth, can be detectable during the play of the game and that such collisions or contact with objects prevent or hinder the patient/user&#39;s dot from moving freely in the virtual environment. For example, the game engine can read a 1-bit (black and white) bitmap picture file, creating an array of logical values, e.g., TRUE (1) or FALSE (0). For example, a logical value of TRUE (1) can correspond to a black pixel (a wall), and a logical value of FALSE (0) can correspond to a white pixel (a path). As long as the patient/user&#39;s dot stays on white pixels, i.e., the path, he/she continues to advance through the maze. Such events limit the movements of hand grasp/release and forearm pronation/supination until the obstacle encountered is negotiated. 
     Knowledge of results and performance are provided continuously as part of the graphical patient interface, to provide the patient/user with a measure of success as well as to encourage the patient/user to do better and more as rehabilitation progresses. For instance, in a goal-oriented game in which the patient/user accumulates points as he/she navigates through a virtual reality environment and/or collects discrete objects, a reward can be provided for achieving a specific score, e.g., point total, during play of the game. 
     For example, the patient/user&#39;s score can increase as the patient/user achieves goals in the game and performs tasks that are required, and can decrease when the patient/user does not perform the tasks in accordance with the rules of the game. For instance, in a scene, if navigation through a virtual maze in the virtual environment is supposed to occur without collisions, the patient/user receives no points and/or losses some or all of the points that he/she has accumulated in the event of a collision. 
     Optionally, visual and/or haptic feedback can be provided to notify the patient/user that he/she has suffered a negative event. Different haptic feedback may be created by defining proper relationship between the position of the handle and the forces experienced by the patient/user. Since the force and torque are under accurate closed-loop control, it is possible to emulate the dynamics of many systems. For example, visual and/or haptic feedback can also be used when a task is performed properly. For instance, as a patient/user navigates through the virtual environment and obtains an object or attains an objective, the graphical patient interface can be programmed to provide an encouraging message or similar reward messages on the screen of the display device  159 , to encourage the patient/user to keep doing the “right things”. 
     Performance data can also be gathered during the game and, in addition to being provided as real-time feedback to the patient/user, can be collected and stored for a later date and/or time for use, for example, by a therapist, clinician, physician, practitioner, and the like, who is skilled in analyzing the data of the therapeutic session, to plan for further rehabilitation sessions. Performance data relate to the characteristics of the movements performed by the subject while accomplishing tasks required by the video games. 
     Of particular interest in this context is monitoring compensatory movement, in which the patient/user uses leverage from other parts of his/her body, e.g., “body English”, to facilitate the game. One might want to discourage this type of movements. Typical compensatory movements would be leaning forward with the trunk, rotating the trunk while performing a pronation (accompanied by internal rotation of the trunk) or supination (accompanied by external rotation of the trunk) movement of the forearm, flexion of the elbow while closing the hand, etc. Movements of these types can be detected using sensor technology that would be combined with the robotic system. The output of the sensors would allow one to detect the performance of compensatory movements and the game could be modify so as to discourage the subject from relying upon compensatory movements. For instance, in the maze game, the walls of the maze could get closer (thus presenting a narrower path to navigate the maze) when people lean forward while playing the game and could move farther apart (thus offering a wider path) when subjects keep their trunk in an appropriate position. 
     Negative behaviors, such as the use of compensatory strategies by the patient/user to achieve a motor goal, can also be discouraged by means of both visual and haptic feedback modalities. Haptic feedback is controlled via the game and provided to the patient/user both as increasing “resistance” to aspects of movements that should be corrected as well as by actively “guiding” the patient/user&#39;s arm or hand to perform the motor tasks properly. 
     The theme and number of potential scenes and games are as limitless as the number of computer games that proliferate in the market today. Basically, a rudimentary virtual reality software scene includes a two-dimensional maze. A velocity model is then applied to the patient/user&#39;s position or icon. The scenes can be time-based or goal-based. 
     Depending on the position or relative position of the handles  163   a  and  163   b , a velocity (vector) and a direction (vector) is applied to the current position or icon. The vector is a combination of the grasp-release motion, which controls y-axis (vertical) velocity, and the supination/pronation motion, which controls x-axis (horizontal) velocity components. These vectors are summed and the resulting vector is applied to the position or icon. 
     The basic feedback on the handles  163   a  and  163   b  includes simulated springs on the handles to guide the patient/user back to a neutral position; the strength, i.e., spring constant, of the spring action can be adjusted to provide greater resistance; and the like. A myriad of additional scenarios can be added to increase the feedback of the system. For example, a modifier can be added to the force feedback as the patient/user&#39;s icon nears the walls, making it more difficult to hit the virtual walls or, alternatively, “steering” the position or icon away from the virtual walls. 
     A second modifier attaches a mass to the patient/user&#39;s position or icon to add inertial effects to the motion. The maze can also include reward/goals and/or traps to avoid in random or specific positions. Rewards and traps work in conjunction with the time- or goal-based scene to motivate patients/users. 
     To accomplish the above, the gaming interface or the controlling device includes at least one of an algorithm, an application, and at least one driver program that is adapted to provide at least one of a collision detection program to read a bitmap picture that is part of a visuomotor integration task, having a plurality of free movement areas and a plurality of no movement areas, and to determine whether an object that is movable as a function of the two degree-of-freedom input data can move commensurate with said input data if movement is to a free movement area or cannot move commensurate with said input data if movement is to no movement area; an additional force field program that increases resistance in the robotic interface when the object approaches any of the plurality of no movement areas; a force/torque program to modulate the two degree-of-freedom input data to achieve a pre-determined force/torque; a feed-forward program that is based on an inverse model for PID control; a sliding mode control program; a model mismatch program to compensate for any mismatch based on the inverse model; and a haptic interaction program that is adapted to define force/torque using a virtual spring, having a spring constant, and a damper, having a damping constant. With the latter, the spring constant of the virtual spring can be positive so as to maintain the object at a neutral position or can be negative so as to make the object deviate from the neutral position. 
     External Hydraulic Circuit and Pump Assembly 
     Referring to  FIG. 1 , inclusion of an external hydraulic circuit  155  in the system  150  expands the functionality of a smart fluid-based actuator. Indeed, the rehabilitation system  150  can operate in several different modes depending on the type of output that is required. These modes of operation can include: a pure damping/braking mode, a counter-flow mode, and an actuator mode. 
     In a pure damping/braking mode, the external hydraulic circuit  155  is inactive, or “passive”; hence, all flow of smart fluid through the main valve is driven solely by force-induced movement of the piston or by the rotating member. The system functionality is completely resistive. Backflow through the external hydraulic circuit  155  can be offset by a controllable external manifold  130  and/or reverse pumping action can be offset by the pump assembly  153  (or can be prevented altogether if the pump type does not allow backflow by design). 
     In a counter-flow mode, the external hydraulic circuit  155  is “active” but the fluid flow direction, which is driven by the hydraulic circuit  155 , flows counter to the fluid flow through the main valve, which is driven by the piston or rotating member. This increases the flow rate of the smart fluid though the main valve. 
     Increased flow rate is particularly helpful when piston velocity is relatively low. Typically, hysteresis effects decrease while the smart fluid changes from a gel to a liquid state. However, artificially increasing the flow rate using the external hydraulic circuit  155  decreases the probability of this happening. In short, in a counter-flow mode, the actuator would operate more like a compressible spring. 
     Finally, in an actuator mode of operation, the external hydraulic circuit  155  is “active” and the direction of smart fluid flow through the main valve is the same as the flow generated by piston action or rotating member action. The effect of the external hydraulic circuit  155  during actuator mode of operation, is, first, to offset the impedance of the system, e.g., friction, viscosity, and so forth, and, then to change the functionality to that of an actuator at higher levels of activation. 
     More particularly, the external hydraulic circuit  155  creates a controllable pressure differential sufficient to cause the vane (whether sliding- or fixed-) to rotate. The main valve operates as a controllable bypass with the advantages of a continuously tunable range and fast response time due to its close proximity to the piston or rotating vane(s). Thus, the output of the system is controlled by adjusting the flow rate of the external pump and the pressure drop across the main valve. The ability to adjust/control the pump flow rate and the smart fluid bypass harmoniously allows for precise control of the output force/velocity of the actuator. 
     Referring to  FIG. 6A  and  FIG. 6B , the hydraulic circuit  155  includes, inter alia, hydraulic lines  41 , a volume compensator (not shown), and a pump assembly  153 . Optionally, the hydraulic circuit  155  can also include a manifold  130 , to control the direction of flow to the actuators  10  and  50  and/or backflow of the smart fluid, and/or to bypass flow to the actuators altogether. The use and need for a manifold  130  (described in greater detail below) depend on the type of pump assembly  153  that is utilized and the response-time requirements for flow direction reversal. 
       FIGS. 12-16  show various diagrammatic views of a rotary vane pump assembly  90 . The pump assembly  90  includes a housing having a lid assembly  91  and a main body  92 , a pressure transducer chamber  93  for taking pressure measurements, a pumping mechanism  110 , and an output shaft  95 . The lid assembly  91  is releasably attached to the main body  92  and, when removed, provides access to the plenum or cavity within the main body  92 . As shown in  FIG. 12B  the lid assembly  91  can include, inter alia, a lid  101  and sealing device, e.g., gasket  102 , for providing a tight seal between the lid assembly  91  and the main body  92 . A low-friction main bearing  104  is provided to center the drive shaft  95 . A sealing device, e.g., shaft seal  103 , provides a tight seal between the lid assembly  91  and the output shaft  95 , to prevent leakage. A spacer  106  is employed to separate the main bearing  104  from the shaft seal  103 . A bearing cover  105  is releasably connectable to the lid  101 , to retain the main bearing  105  and shaft seal  103  in place. 
       FIGS. 13A, 13B, and 14  show diagrammatic views of the pumping mechanism  110 . The pumping mechanism  110  is mechanically coupled to the drive shaft  95  and includes a plurality of vanes  111  that are disposed radially about the axis of the pump drive shaft  95 . The vanes  111  are spring loaded to provide translational movement in the radial direction. For example, vane  111   a  shows a fully-extended vane; vane  111   b  shows a fully retracted or depressed vane; and vane  111   c  shows a partially extended (or partially depressed) vane. 
     Volume compensation channels  114  are provided adjacent to and on either side of each vane  111 . Volume compensation channels  114  are structured and arranged to allow fluid to escape from a first pump chamber  107   a  into an adjacent pump chamber  107   b  as a vane  111  is radially depressed. More specifically, as the cam  99  ( FIG. 15 ) forces a vane  111  radially inward, a volume compensation valve  115  corresponding to the vane being depressed  111  connects both sides of the volume compensation chamber, allowing fluid to escape and, thereby, equalizing pressure between adjacent zones. When the vane  111   a  is fully extended, e.g., when it becomes the “active vane”, or fully depressed, the volume compensation valve  115  is completely closed. 
       FIG. 16  shows a diagrammatic detail of a vane  111 . The vane  111  includes a volume compensation valve  115 , an alignment feature  116 , e.g., a cylindrical alignment feature to keep the vane aligned and in position, and a spring location  117 . A small spring (not shown) is disposed in the spring location  117  and biased to hold the distal edge  118  against the periphery of the cam  99  during depression and extension cycles. 
       FIGS. 14 and 15  show the interior components of the pump assembly  90  and the pumping mechanism  110 . The pump chambers  107  correspond to zones of positive or negative fluid pressure. Each vane  111  forces fluid into the input/output chambers  108  and into the main valve  109 . The pressure transducer runners  93  lead into the input/output chambers. 
     At the center of the runner  93  is a differential pressure sensor which measures the difference in pressure between adjacent pump chambers  107 . The pressure differential (P) multiplied by the area of the exposed vane (A) is equal to the force (F) on the vane  111 . This force can be integrated over the radius of the pumping mechanism  110  to provide an estimate of the torque. 
     Because the individual vanes  111  are constantly moving in and out of the pump chamber  107 , a valve system  109  was devised. This valve  109  allows the fluid below the vane  111  to escape into the chamber  107 . Because the volume of the fluid below the vane  111  is equal to the volume of the vane  111 , the system&#39;s volume stays constant which enables the system to operate in a closed manner. 
     Piezoelectric Transducer-Based, High-Speed, Hydraulic-Control Manifold (Optional) 
     An (optional) high-speed, hydraulic-control manifold can be integrated into the hydraulic circuit  155 , to control the direction and rate of fluid actuation more effectively. Although a manifold  130  can be driven electrically by solenoids, piezoelectric transducers, mechanically by levers or buttons, and so forth, the invention will be described using a piezoelectric transducer-based manifold  130 . Advantageously, the piezoelectric transducers can be encapsulated in a compliant material to facilitate both sealing and flexing. Those skilled in the art, however, can appreciate how to adapt alternative driving means in like manner as with the piezoelectric transducers. 
     Referring to  FIGS. 17-23 , a manifold  130  comprising a manifold block  140  and having a low-pressure side  138  and a high-pressure side  139  is shown. Each of the low- and high-pressure sides  138  and  139  includes a plurality of (e.g., two) valves  135  that are fluidly coupled to an actuator via inlet/outlet ports  132 . Each low- and high-pressure sides  138  and  139  is also fluidly coupled to the hydraulic circuit  155  (and the pump assembly  156 ) via an inlet/outlet port  131 . A bypass  137  provides internal fluid communication between the low-pressures side  138  and the high-pressure side  139 . A volume compensator  136  (described in greater detail below) is provided in the low-pressure side  138 . 
     The valves  135  are piezoelectric transducers that are encapsulated in a compliant material to facilitate both sealing and flexing. Biasing member, e.g. springs  134 , are mechanically coupled to a stationary rod(s)  133  that is/are disposed within the pressure chamber portions  141  and  142  and are, further, adapted to apply the needed biasing forces to maintain the valves  135  in a normally-closed (NC) position. 
     Referring to  FIG. 19 , the operation of the manifold  130  in an actuator mode of operation in a forward direction will be described. Smart control fluid from the hydraulic circuit  155  is pumped into or otherwise flows into the chamber portion  142  of the high-pressure side  139  of the manifold  130  via inlet/outlet port  131  (point B), whence the smart fluid is routed to one or more of the actuators via inlet/outlet port  132  (point D). 
     Smart fluid returns from the actuator(s) to the low-pressure side  138  of the manifold  130  via inlet/outlet port  132  (point C). The volume compensator  136  in the low-pressure side  138  allows for changes in volume resulting from shaft motion, thermal expansion/contraction of the smart fluid, and the like. The volume compensator  136  can include, for example, a deformable elastic diaphragm that deforms to compensate for the volume change by changing its own volume. After volume compensation is completed, the smart fluid is pumped back into or otherwise flows back into the hydraulic circuit  155 , e.g., via inlet/outlet  131  (point A). 
     Referring to  FIG. 20 , the operation of the manifold  130  in an actuator mode of operation in a reverse direction will be described. Smart fluid from the hydraulic circuit  155  again enters the chamber portion  142  of the high-pressure side  139  of the manifold  130  via inlet/outlet port  131  (point B), whence the smart fluid is routed to one or more actuators via inlet/outlet port  132  (point F). 
     Smart fluid returns to the low-pressure side  138  of the manifold  130  via inlet/outlet port  132  (point E), where the volume compensator  136  allows for changes in volume resulting from shaft motion, thermal expansion/contraction of the smart fluid, and the like. After volume compensation is completed, the smart fluid passes back into the hydraulic circuit  155 , e.g., via inlet/outlet  131  (point A). 
     Referring to  FIG. 21 , the operation of the manifold  130  in a damper/brake mode of operation in a forward direction will be described. For damping/braking, the high-pressure side  139  is closed off. Smart fluid from the hydraulic circuit  155  enters the chamber portion  141  of the low-pressure side  138  of the manifold  130  via inlet/outlet port  132  (point E) where the volume compensator  136  allows for changes in volume resulting from shaft motion, thermal expansion/contraction of the smart fluid, and the like. 
     Referring to  FIG. 22 , the operation of the manifold  130  in a damper/brake mode of operation in a reverse direction will be described. For damping/braking, the high-pressure side  139  is again closed off. Smart fluid from the hydraulic circuit  155  enters the chamber portion  141  of the low-pressure side  138  of the manifold  130  via inlet/outlet port  132  (point C) where the volume compensator  136  allows for changes in volume resulting from shaft motion, thermal expansion/contraction of the smart fluid, and the like. 
       FIG. 23  shows the manifold  130  in a bypass mode of operation. All of the valves  135  in both the low-pressure and high-pressure sides  138  and  139  are closed. Smart fluid from the hydraulic circuit  155  enters the chamber portion  142  of the high-pressure side  139  and travels directly to the chamber portion  141  of the low-pressure side  138  via the bypass  137  (point G) before the smart fluid passes back into the hydraulic circuit  155 , e.g., via inlet/outlet  131  (point A). 
     The bypass mode allows the manifold  130  to react quickly to changing commands/modes while the pump is running. The master flow rate can be controlled both by the pump and by the level of bypass. It should be noted further that the bypass valve  137  as well as the other valves  135  can be proportionally controlled, so that the manifold  130  can operated in a hybrid mode. The hybrid mode combines the principle modes of operation, i.e., actuator, damper, and bypass. Each combined mode and its respective level of pump flow and valving will give the actuator/damper/brake a different “feel”. 
     Power Supply 
     Depending on whether the smart fluid used is influenced by changes in field strength of a magnetic field or by changes in the field strength of an electric field, the system  150  includes a power supply  154  that provides current or high-voltage, respectively. The invention has been described assuming that the smart fluid is an electro-rheological fluid (ERF); hence, the power source  154  would supply high-voltage to generate an electric field. The selection of ERF is arbitrary and is for illustrative purposes only and is not made to be limiting or exclusive of other smart fluids. Those of ordinary skill in the art can apply the teachings of this disclosure to other smart fluids. 
     Data Acquisition and Controlling System 
     Although the gaming engine determines how the rehabilitation system should behave, it is the controller that receives data, e.g., from the sensing devices associated with the robotic interface  151 , the hydraulic system  153 , the gaming engine  152 , and so forth, and that generates signals, e.g., to the patient/user&#39;s interface, to the practitioner&#39;s interface, and so forth, to ensure that the system functions properly and seamlessly. 
     A framework for the controlling system  156  is shown in  FIG. 24A  and  FIG. 24B . The control hardware of the rehabilitation system  150  can include a primary, or “host”, controller  31  and a secondary, or “real-time target” (RTT), controller  32 . The host controller  31  can be a personal computer, e.g., laptop computer, conventional desk top computer, and the like. The real-time target (RTT) controller  32  should be adapted to run a real-time operating system (RTOS). 
     More particularly, regular data acquisition (DAQ) hardware running on a general-purpose operating system (OS) e.g., Windows® by Microsoft®, cannot guarantee real-time performance since factors, such as programs running in the background, interrupts, and graphical processes, can compromise performance. In contrast, real-time hardware running a real-time operating system (RTOS) allows a programmer to prioritize tasks so that the most critical task always take control of the processor when needed. This property enables reliable applications with predictable timing characteristics. 
     The primary controller  31  is structured and arranged to store and/or execute (run) the major software programs needed for the system to operate properly. For example, the software can include software for visualization of a game, e.g., Panda 3D, as well as software for providing communication between the primary  31  and the secondary controllers  32 , e.g., LabVIEW. 
     The host controller  31  further includes hardware or software for displaying patient/user and practitioner graphic user interfaces (GUIs), e.g., on display devices  159   a  and  159   b . To reduce costs and enhance portability, board level RT targets that feature FPGA chips and single board computers can be used. These solutions offer a significant packaging advantage at the expense of flexibility. 
     The secondary controller  32  is structured and arranged to control the rehabilitation system  150  itself. To this end, the RTT controller  32  communicates with the rehabilitation system  150  through a data acquisition card  94 . A non-exhaustive list of the various functions performed by the secondary controller  32  includes data acquisition, system control, and so forth. The algorithms, software, driver programs, applications and the like of the hand rehabilitation system  150  are run on the real-time platform, i.e., the RTT controller  32 , allowing accurate timing characteristics to the system  150 . 
     The RTT controller  32  further communicates with the host controller  31 , to transmit data and critical parameters thereto. Communication between the host controller  31  and the RTT controller  32  is via high speed Ethernet  96 . Machine code can be developed on the host controller  31 , and then deployed to the RTT controller  32 . Those of ordinary skill in the art can appreciate that a single controller or more than two controllers may be used. Cost, size, and power requirements, inter alia, will determine an optimal number of controllers. 
     For example, the force and position sensors that provide data about the actuators transmit output signals to the host controller  31  via the RTT controller  32 . In response the host controller  31  routs commands to the various components of the rehabilitation system  150  through the RTT controller  32 . For example, the operation of an actuator is controlled by two command inputs: the strength of the electric field applied across the electrodes and the flow rate of the control fluid provided by the pump assembly. Hence, the host controller  31  is adapted to increase/decrease the current or high-voltage from the high-voltage power supply to the electrodes of the actuators  10  and  50  and also to control the speed and direction of the pump assembly  153 . The pump assembly  153  facilitates the “active” behavior of the system  150  and the high-voltage power supply  154  provides the electric field (or magnetic field) that controls the behavior of the smart ERF (or MRF). 
       FIG. 40  shows an illustrative control diagram for spring effect of the conventional actuator embodiment shown in  FIGS. 37-39 . The magnitude of the applied force (F) and the position or relative position (x) of the handle assembly are important variables. As a result, the controller  31  is structured and arranged to provide appropriate input signals to various components of the system  150  that will result in the specified output of the actuator(s). 
     For example, force (F) is proportional to the displacement (x) of a spring with a known, fixed spring constant (k). hence, once a displacement (x) is measured by the sensing devices, e.g., linear potentiometers, the magnitude of the required force (or torque) can be fed into an inverse model  95  of the system while simultaneously or substantially simultaneously the desired force and the measured force are compared in a proportional feedback controller  98 . Results from the proportional feedback controller and the inverse model  95  are combined to provide a needed electric field strength to activate the linear motor. Knowing this, a high-voltage requirement is computed, which the power supply delivers. 
     In other applications, the host controller  31  is further structured and arranged to include friction compensation, an integral controller for zero steady state error, an adaptive or robust control for guaranteed stability and performance under varying system conditions. 
     Although the invention is described through the above-described exemplary embodiments, it will be understood by those of ordinary skill in the art that modifications to, and variations of, the illustrated embodiments can be made without departing from the inventive concepts disclosed herein. Accordingly, the invention should not be viewed as limited, except by the scope and spirit of the appended claims.