Abstract:
A compact four degrees of freedom parallel mechanism suitable for use as a hand control or wrist is provided that has backdrivability, is singularity free and has a large workspace and a large force reflecting capability. The structure is light but rigid, and the electric actuators are all placed on the ground or base and provide independent control of each degree of freedom. Each degree of freedom is connected to an actuator either directly or through a cable drive system. The first two degrees of freedom are created by two identical pantographs pivoted together on pivoted joints to define a hemispherical motion of an object (end point) about a center point (hemisphere center). The third and fourth degrees of freedom represent rotation and sliding motions of the object around and along the radius of the created hemisphere, respectively. The axes of these latter degrees of freedom are concentric, and these axes intersect with the axis of the pantographs pivoted joints at the hemispheric center.

Description:
FIELD OF INVENTION 
     The present invention relates to a three or four Degree of Freedom (DoF) structure that may be used as a hand controller or haptic to be manipulated (preferably with force feedback) and/or a wrist structure the movement of which is to be controlled. 
     BACKGROUND OF THE PRESENT INVENTION 
     The concept of remote control in the medical field for diagnosis and or other operations to be performed by a Doctor on a remote patient is gaining more and more acceptance as it may be used to overcome serious problems of availability particularly in areas of low population insufficient to support locally a doctor having specific expertise. For Example, accurate assessment of abdomen and interpretation of abdominal pain are difficult, particularly for the inexperienced clinician or nurse. Errors and uncertainty can lead to delays in diagnosis and even death, as in appendicitis. These difficulties are amplified for remote patients who may have less timely and unequal access to expert clinical care. Although there is considerable interest and research in palpation technique in telehealth applications, currently there is no system equipped with kinematically similar configurations hand controller and robotic wrist that permits distant clinical palpation. This includes abdominal examination as well as ultrasound diagnosis, which require expert assessment and are a frequent cause of patient transfer. 
     Haptic controllers and wrists of many different forms have been proposed and used in controlling wrist that may but need not be of similar construction. 
     With respect to the design of hand controllers or haptic devices for medical procedures, the haptic devices developed by Rosenberg et al. (see U.S. Pat. No. 5,721,5665, 805,140, 6,271,833) and Bevirt et al., U.S. Pat. No. 6,024,576, have all two degrees of freedom providing two rotations about a fixed point (also termed center-of-rotation). They all have simple parallel structures. Additional extra degrees of freedom to these devices will unusually enlarge them or will require the actuators not to be grounded (i.e., become non-floating). Similarly, the force feedback mechanisms by Martin et al., U.S. Pat. No. 6,104,382, and Rosenberg, U.S. Pat. No. 6,154,198, have only two degrees of freedom providing two rotations about a fixed point and use a parallel structure. 
     The three DoF parallel linkage by Adelstein, U.S. Pat. No. 5,816,105, provides three translational displacements of the end point. The haptic device by Mor, U.S. Pat. No. 6,088,020, has three active and two passive degrees of freedom. It does not have a fixed remote center-of-rotation. The adjustable surgical stand by Faraz et al., shown in U.S. Pat. No. 5,824,007, includes two separate pantographs each providing spherical motion about fixed points. It uses a serial linkage mechanism and the actuators are not grounded. 
     Birglen et al. in Birglen, L., Gosselin, C., Pouliot, N. (2002), “Shape, a new 3 DoF haptic device”, IEEE Transactions on Robotics and Automation; 18(2) 166–175, reported the development of three degrees of freedom haptic device using a spherical parallel mechanism. 
     Duriez et al. in Duriez, Ch., Lamy, D., Chaillou, Ch. (2001), “A parallel manipulator as a haptic interface solution for amniocentesis simulation”, proceedings IEEE International Workshop on Robot and Human Interactive Communication, describes the development of a parallel robot for simulating the terminal organ that moves on a spherical surface with variable radius. 
     The PantoScope by Baumann et al., in Baumann, R., Maeder, W., Glauser, D., Claval, R. (1997), “The PantoScope: a spherical remote center-of-motion parallel manipulator for force reflection”, proceedings IEEE International Conference on Robotics and Automation, describes the use of two non-identical pantograph-like mechanisms to build a parallel, spherical, remote center-of-motion manipulator with force reflecting capabilities. The use of non-symmetrical pantographs, however, works against the uniformity requirement [see paper by Hayward, V. (1995), “Toward a seven axis haptic device”, proceedings IEEE International Conference on Intelligent Robots and Systems], which may degrade the performance of the device. 
     The six degrees of freedom haptic devices by Lee et al. [see Lee, J. H., Eom, K. S., Yi, B. J., Suh, I. H. (2001), “Design of a new six Dof parallel haptic device”, proceedings IEEE International Conference on Robotics and Automation], and Yoon and Ryu [see Yoon, J., Ryu, J. (2001), “Design, fabrication, and evaluation of a new haptic device using a parallel mechanism”, IEEE/ASME Transactions on Mechatronics 6 (3): 221–230], use non-floating actuators, but to keep the remote center-of-motion at a prescribed location, all degrees of freedom need to be active. 
     U.S. Pat. Nos. 6,339,969 and 6,368,332 both to Salcudean et al., each discloses a device having several degrees of freedom each employing a plurality of pantographs to control the movement of an end point and one of which has been specifically designed for assisting a surgeon in performing. 
     With respect to the design of novel robotic wrists, Stanisic et al. in U.S. Pat. No. 6,026,703 and the paper Wiitala, J., Stanisic, M. M. (2000), “Design of an overconstrained and dexterous spherical wrist”, ASME Journal of Mechanical Design. 122: 347–353, describe a wrist structure formed with a dexterous split equator joint device with all points of all links moving on spheres. Thus, there is no remote center-of-motion outside the mechanism. 
     Compact wrist actuators by Rosheim described in U.S. Pat. Nos. 4,686,866, 4,723,460 and 6,418,811 have three degrees of freedom with linear actuators. These devices provide spherical motion of an end point about a fixed point, which is inside the mechanism. The spherical robotic wrist by Dien et al., U.S. Pat. No. 4,628,765, consists of two perpendicular semi-circular yokes to provide a spherical motion, with no remote center-of-motion. The yokes can be heavy, need precision machining and usually exhibit backlash. The stereotactic apparatus for locating or removing lesions developed by Shelden et al. and described in U.S. Pat. No. 4,638,798, provides the required motions for ultrasounds and palpation. The actuators in this device, however, are floating (i.e., they are placed at the moving joints) making it bulky and heavy. 
     The wrist for detecting very small breast anomalies by Souluer, U.S. Pat. Nos. 6,192,143; 6,351,549; and 6,400,837, consists of a positioning device, fully adjustable bed and a detection head, which should work together to position/orient the probe over the breast for palpating. The device is not only big, but also cannot provide the required motion for ultrasound diagnosis. 
     Funda et al., U.S. Pat. No. 6,201,984, developed a remote center-of-motion device for endoscopic surgery. The device provides a spherical motion about a fixed point with two circular guides. Available circular guides are bulky, heavy and difficult to be machined precisely. The actuators are also floating, which would not fulfil the requirements of the wrist design for the purpose of the preferred applications of the present invention. 
     The remote center-of-motion robot for surgery by Taylor et al., U.S. Pat. No. 5,397,323, has four degrees of freedom and uses a serial linkage mechanism. All the actuators are mounted on the proximal part of the device (not on the ground) and located on the same plane as the work point. Thus, it is not easy to install this device on the implement of a manipulator. The Black Falcon instrument by Madhani et al. described in the paper by Madhani, A. J., Niemeyer, G., Salisbury, K. (1998), “The Black Falcon: a teleoperated surgical instrument for minimally invasive surgery”, proceedings IEEE/RSJ International Conference on Intelligent Robots and Systems, and the Laparoscopic positioning manipulator described in Faraz, A. and Payandeh, Sh. (1998), “A robotic case study: optimal design for laparoscopic positioning stands”, in International Journal of Robotics Research 17 (9): 986–995, have similar structures as the one belonging to Taylor et al. (see U.S. Pat. No. 5,397,323 referred to above). 
     The laproscopic workstation by Cavusoglu et al. described in Cavusoglu, M. C., Tendick, M. C., Sastry, S. Sh. (1999), “A laparoscopic telesurgical workstation”, IEEE Transactions on Robotics and Automation 15 (4): 728–739, uses three linear actuators with grounded motors (but appear to be coupled) for the first three degrees of freedom and one floating actuator for the fourth degree of freedom. 
     The parallel mechanism by Vischer and Clavel described in Vischer, P., Clavel, R. (2000), “Argos: A novel 3-DoF parallel wrist mechanism”, International Journal of Robotics Research 19 (1): 5–11, provides three degrees of freedom rotational motion about a fixed working point. However, the remote center-of-motion is enclosed within the mechanism at some configurations. The roll motion is also limited to 120 degrees. 
     The paper by Hamlin, G. J., Sanderson, A. C. (1994), “A novel concentric multilink spherical joint with parallel robotics applications”, proceedings IEEE International Conference on Robotics and Automation, teaches the use of a pantograph mechanism to built novel spherical joints. 
     Degoulange et al. [see the paper by Degoulange, E., Urbain, L., Caron, P., Boudet, S., Megnien, J. L., Pierrot, F., Dombre. E. (1998), “HIPROCRATE: an intrinsically safe robot for medical applications”, proceedings IEEE/RSJ International Conference on Intelligent Robots and Systems], reports a device for ultrasound diagnosis; however, all joints are in motion during the tasks. Similarly, Salcudean et al., U.S. Pat. No. 6,425,865 [see also the paper by Zhu, W. H., Salcudean, S. E., Bachmann, S., Abolmaesumi, P. (2000), “Motion /force/image control of a diagnostic ultrasound robot”, proceedings IEEE International Conference on Robotics and Automation, and the paper by Salcudean, S. E., Zhu, W. H., Abolmaesumi, P., Bachmann, S., Lawrence, P. D. (2000), “A robot system for medical ultrasound”, proceedings 9 th  International Symposium of Robotics Research (ISRR&#39;99)], designed and constructed complete robots for moving ultrasonic probes on the patient&#39;s skin with a given force. Accurate palpating of the probe along the roll axis, however, can only be made by the rotation of the entire parallelogram linkage about two perpendicular axes of rotation, and translation of the entire robot over a table. Although the system is counterbalanced and backdrivable, motors are non-floating and the inertial effect of the system is not negligible. 
     The design by Masuda et al. as described in the paper by Masuda, K., Kimura, E., Tateishi, N., Ishihara, K. (2001), “Three dimensional motion mechanism of ultrasound probe and its application for tele-echography system”, proceedings IEEE/RSJ International Conference on Intelligent Robots and Systems, requires the whole mechanism to sit on patient. As such the workspace is limited. Also, for orienting the probe about a fixed point on the attention skin, all joints need to move. 
     The wrist by Gourdon et al. described in Gourdon, A., Poignet, Ph., Poisson, G., Vieyres, P., Marche, P. (1999), “A new robotic mechanism for medical application”, proceedings IEEE/ASME International Conference on Advanced Intelligent Mechatronics, uses gears that affects the backdrivability of the system and generates backlash and also have coupled degrees of freedom. 
     The European ‘OTELO’ project discussed in Guerin, N. S., Bassit, L., Poisson, G., Delgorge, C., Arbeille, Ph., Vieyres, P. (2003), “Clinical validation of mobile patient-expert tele-echography system using ISDN lines”, Proceedings IEEE-EMBS Information Technology Applications in Biomedicine; also in Delgorge et al. (2002) “OTELO project: mObile Tele-Echography using an ultra-Light rObot”, proceedings Telemed&#39;02, describes the development of a four degree-of-freedom wrist with a remote center-of-motion. In their design, in order to produce a single pitch or yaw motion, two degrees of freedom must work cooperatively. Some of the motors are also floating. As a result, the conical workspace is limited. The wrist also has a singular configuration inside its workspace. The European ‘TER’ project described in Gonzales, A. V., et al. (2001). “TER: a system for robotic tele-echography”, proceedings International Conference of Medical Image Computing and Computer Assisted Intervention, describes the development of a robotic tele-echography system that uses parallel configuration based on pneumatic artificial muscles. The system appears to be bulky with limited workspace. Furthermore, the device entirely embraces the patient and there is no reasonable access to the patient in emergency cases. 
     Mitsubishi et al. as described in Mitsubishi M., Warisawa, Sh., Tsuda, T., Higuchi, T., Koizumi, N., Hashizume, H., Fujiwara, K. (2001), “Remote ultrasound diagnostic system”, proceedings International IEEE Conference on Robotics and Automation, have developed a telerobotic system consisting of circular guides connected in a serial configuration and embedded with gears of high ratios. The mechanism is heavy, large (it has a size of a human trunk) and is therefore not mobile. Also, it does not appear to be backdrivable due to the use of semi circular spur gears moved by small pinions. 
     BRIEF DESCRIPTION OF THE PRESENT INVENTION 
     It is the main object of the present invention to provide a four DoF structure that may function as a hand controller and/or as a wrist mechanism. 
     It is an object of the present invention to provide a telerobotic system that may be used for diagnosis and/or other operations to be performed by a doctor or physician on a remote patient. Preferred applications of the invention are in the areas of Distance Abdominal Palpation (DAP) and Distance Ultrasound Diagnosis (DUD). The DAP-DUD system will primarily be used in situations wherein a bedside expert is not available. This allows patients who would normally be transferred to the location of the specialist, to be examined by the specialist without having to travel. Thus, the services and information will be delivered to individuals in many cases without leaving their own communities. 
     It is a further objective of the present invention to provide an improved hand controller or haptic. 
     It is yet another objective to provide an improved wrist structure. 
     Preferred Form of Hand Controller 
     A desktop compact three or four degrees of freedom mechanism suitable for use as a hand control is provided that preferably has backdrivability, is singularity free and has a large workspace and a large force reflecting capability. The structure is light but rigid, and the actuators are all placed on the ground or base and provide independent control of each degree of freedom. Each degree of freedom is connected to an actuator either directly or through a cable drive system. The first two degrees of freedom are created by two identical pantographs pivoted together on pivoted joints to define a hemispherical motion of an object (end point) about a center point (hemisphere center). The third and fourth (if provided) degrees of freedom represent sliding and rotational motions, respectively, of the end point object along and around the radius of the hemisphere created by the first and second degrees of freedom. The axes of these latter (third and fourth) degrees of freedom are concentric, and these axes intersect with the axis of the pantographs pivoted joints at the hemispheric center. 
     The third degree of freedom preferably is obtained using a cable drive and a slider in combination with a ball spline shaft that converts the rotating motion of an inner universal joint into sliding movement of the object (end point) through a pair of decoupling ball bearings. 
     The fourth degree of freedom preferably is obtained using a tube in combination with the ball spline nut that transmits the rotational motion of an outer universal joint to the end point or object. Sliding behavior of the ball spline in combination with a ball bearing is used to decouple the third and fourth degrees of freedom from each other. Another ball bearing is used to decouple the rotational motion of the ball spline nut from the pantographs pivoted joint. The moving object (which in normal operation is held by the expert) is attached to the end of ball spline shaft and preferably is configured so that it can be held in two places while being manipulated. 
     Preferred Form of Wrist 
     The wrist may have up to four degrees of freedom. The first two degrees of freedom are created by two identical pantographs pivoted together to define a spherical motion of a probe about a fixed point i.e. a created hemisphere. The third degree of freedom can be either sliding along the radius of the created hemisphere or rotation around it, to define a roll motion. Or, the wrist may incorporate both sliding and rotation to provide four degrees of freedom. Different modules may be mounted on the wrist to provide the third, and/or third and fourth degrees of freedom of the wrist. 
     One module that provides sliding motion incorporates a telescopic double universal joint and accommodates the first two degrees of freedom. This construction can be used for palpating over an abdomen by pressing a probe or end point in a desired orientation. A second module may be used to perform both the roll (rotating) and sliding motion bringing the total number of degrees of freedom to four. This construction when used for applying ultrasound allows a probe or end point such as an ultrasound device to be three-dimensionally oriented about the fixed point (center point) while being pressed on the patient&#39;s body similar to the standard hand movements of the clinical expert. 
     All degrees of freedom are kinematically decoupled and are controlled by actuators (electric motors) that are fixed to the base of the wrist and are located away from the patient. 
     The power from each actuator is preferably transmitted to the driven axis by cables allowing the mechanism to be backdrivable. This not only allows easy measurements of the output force at the actuator sides, but also allows the probe to be passively pushed back by the patient in emergency circumstances. The mechanism exhibits a singular free, low friction, zero backlash, compact, rigid motion with a high-sustained output force. 
     Broadly, the present invention relates to a hand controller or wrist device comprising a base and a moveable portion moveable relative to said base, said moveable portion having a main longitudinal axis and an end point, a pair of pantographs each formed by a plurality of pivotably interconnected links arranged for pivotal movement in a plane, 
     said planes being mutually perpendicular, means for pivotably mounting each said pantograph adjacent to one of its ends for rotational movement on its pivotal axis relative to said base in a direction substantially perpendicular to its plane and coupling means connecting each of said pantographs adjacent to its end remote from its one end to move said end point in a hemispherical path about a center point when said pantographs are pivoted on their said means for pivotably mounting, said pantographs defining a first and a second degree of freedom of said end point; 
     said center point being defined by the intersection of said pivotal axes and said main longitudinal axis, 
     an inner universal joint, 
     said inner universal interconnecting a first inside element and a second inside element forming a pair of inside elements that define a third degree of freedom of said end point, said first of said inside elements including a pair of portions and means for translating axial movement substantially parallel to said main axis of one of said pair portions of said first inner element to rotational movement of a second portion of said pair of portions of said first inner element and vice versa while permitting relative rotational movement between said one and said second portions, said end point being connected to said one portion of said one of said second pair of elements and 
     means for mounting said second inside element for rotation about it axis relative to said base; 
     said coupling means connecting said pantographs to said one portion while permitting movement of said one portion relative to said pantographs. 
     Preferably, said device further comprises an outside universal joint concentric with said inside universal joint combines with said inside universal joint to provide a pair of concentric universal joints, said outside universal joint interconnecting a first outside element and second outside element that form a pair of outside elements; and means coupling said first outside element to said one portion of said first inside element to prohibit relative rotational movement while permitting relative axial movement between said one portion and said first outside element. 
     Preferably, said pair of outside elements define a fourth degree of freedom of said end point. 
     Preferably, said device is a controller and said center point and said inner universal joint pivot point are in the same location. 
     Preferably, said device further comprises a separate actuator for each of said degrees of freedom and each said actuator is supported on said base. 
     Preferably, said device is a controller and said actuators provide force feedback to said end point in each of said degrees of freedom and said center point is defined by the intersection of said pivotal axes and said main longitudinal axis and said end point is moved about said center point by operation said degrees of freedom. 
     Preferably, said actuator for said third degree of freedom is coupled to said second inside element and through said inner universal joint to said second portion of said first inside element. 
     Preferably, said means for translating axial movement to rotational movement and vice versa include a belt type drive which includes a pulley formed by a pulley that rotates with said second portion and a belt having a path of travel parallel to said axial movement and connected to said one portion so that movement of said belt moves said one portion substantially axially. 
     Preferably, said actuator for said fourth degree of freedom includes a belt type drive coupling with said second outside element of said pair of outside elements and through said outside universal joint with said first outside element of said pair of outside elements. Preferably, said device is a wrist and said actuators drive said end point in each of said degrees of freedom. 
     Preferably, said means for mounting said second inside element for rotation about it axis includes a second inside universal joint, said second inside universal joint coupled on one side to said second inside element and its other side is rotatably mounted on said base. Preferably, a second outside universal joint concentric with said second inside universal joint combines with said second inside universal joint to provide a second pair of concentric universal joints, said second outside universal joint coupled on one side to said second outside element and its other side is rotatably mounted on said base. 
     Preferably, said actuator for each of said first and second degrees of freedom includes a belt type drive, drivingly interconnecting its respective said means for pivotably mounting with its actuator. 
     Preferably, said actuator for said third degree of freedom is coupled to one side of said second inside universal joint and another side of said second inner universal joint is connected to said second inside element and through said inner universal joint to said second portion of said first inside element. 
     Preferably, said actuator for said fourth degree of freedom includes a belt type drive coupling with one side of said first outside universal joint. 
     Preferably, said means for translating axial movement to rotational movement and vice versa includes a worm type gear. 
     Preferably, said one portion is a module. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Further features, objects and advantages will be evident from the following detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings in which; 
         FIG. 1  is an isometric representation of the present invention showing the haptic (hand controller) and the wrist in different physical locations to illustrate control of the wrist from a location remote from the wrist. 
         FIG. 2  is an isometric illustration of a preferred form of the present invention for use as a hand controller. 
         FIG. 3  is an isometric illustration with parts omitted showing the pantographs for applying the first and second Degree of Freedom (DoF) to the manipulated end point. 
         FIG. 4  is an isometric illustration with parts omitted showing one preferred arrangement for applying the third DoF to the manipulated end point. 
         FIG. 5  is an isometric illustration with parts omitted showing in greater detail the belt drive system for applying the third DoF to the manipulated end point shown in  FIG. 4 . 
         FIG. 6  is an isometric illustration of one form of adjustment mechanism for adjusting the tension in the belt drive for the third degree of freedom. 
         FIG. 7  illustrates the interconnection of the pulley mounting for the third degree of freedom with the sleeve connected to one of the pantographs of the first and second degrees of freedom. 
         FIG. 8  is an isometric illustration with parts omitted showing a preferred arrangement for delivering rotational movement to the end point i.e. for applying the fourth DoF to the manipulated end point. 
         FIG. 9  is an isometric cross-section illustration with parts omitted showing inter-relationship of the elements for applying the third and fourth DoF to the end point. 
         FIG. 10  is an isometric illustration with parts omitted showing in greater detail the connection between the pantographs for the first and second DoF to the manipulated end point. 
         FIG. 11  is a schematic illustration of the movements of the end point. 
         FIG. 12  is a general isometric illustration with some parts omitted showing the wrist structure of the present invention. 
         FIG. 13  is a general side elevation view of a preferred form of the device of the present invention for use as a wrist. 
         FIG. 14  is an isometric illustration with parts omitted showing the location of the center-of-motion of the device. 
         FIG. 15  is an isometric illustration with parts omitted showing in greater detail one of the pantographs for applying the first or second DoF movements of the end point. 
         FIG. 16  is an isometric illustration with parts omitted showing the belt drive arrangement for applying the driving forces to or from the pantograph(s) for controlling the first and second degrees of freedom DoF of the preferred form of wrist device. 
         FIG. 17  is an isometric illustration with parts omitted showing the support arrangement for the cable drive arrangement pantographs for the preferred form of wrist device. 
         FIG. 18  is an isometric sectional view with parts omitted showing the drive arrangement for applying the third DoF to the end point. 
         FIG. 19  is an isometric with parts omitted showing the drive arrangement for applying the fourth DoF to the end point. 
         FIG. 20  is an isometric with parts omitted similar to  FIG. 19  but showing the drive arrangement for applying the fourth DoF to the end point in a different orientation. 
         FIG. 21  is an isometric view with parts omitted showing the base end of the drive arrangement for applying the third and fourth DoF to the end point of the wrist. 
         FIG. 22  is an isometric sectional view with parts omitted showing part of the drive system for the fourth degree of freedom of the wrist. 
         FIG. 23  is an isometric sectional illustration with parts omitted showing a wrist module (probing assembly) for mounting in the wrist assembly for applying four degrees of freedom. 
         FIG. 24  shows the detailed isometric sectional illustration with parts omitted showing a wrist module (probing assembly) for mounting in the wrist assembly for applying four degrees of freedom mounted in the wrist assembly. 
         FIG. 25  is an isometric sectional illustration with parts omitted showing a wrist module (probing assembly) for mounting in the wrist assembly for applying only three DoF. 
         FIG. 26  is an isometric sectional illustration with parts omitted showing a wrist module (probing assembly) for mounting in the wrist assembly for applying three DoF mounted in the wrist assembly. 
         FIG. 27  is a schematic illustration similar to  FIG. 11  but showing the movements of the probe or end point of the embodiment of  FIGS. 12 to 26 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention has many applications including those in the area of telerobotic and ultrasound/palpation procedures for which it is particularly adapted. As indicated in  FIG. 1  the patient  1  is positioned on an examining table  7  at a location remote from the expert (physician)  2  who maneuvers the haptic or controller  10  mounted on a suitable table or base  4 . In the illustrated arrangement the physician is showing using only one arm  6 , but it will be apparent that either arm or both arms may be used. The controller  10  is held by a clinical expert and provides three or four degrees of freedom for orienting and positioning the wrist  10 A which is mounted on a platform  5  with prismatic motion which is positioned by a stand  3  in overlying relationship to the patient  1  lying on table  7  at the location remote from the expert  2 . The hand controller  10  reflects the sensed forces applied against of from the patient  1  to the physician&#39;s  2  hand i.e. the hand controller is provided with force feedback in known manner. The invention thus may be used to improve health care in rural and urban sites, where distance is a critical factor. 
     Preferred Form of Hand Controller 
     The first embodiment of the present invention illustrated in  FIGS. 2 through 11  inclusive and the second embodiment illustrated in  FIGS. 12 through 27  are devices  10  (or  10 A) that may function either as wrists or as controllers such has hand controller or joysticks. 
     The device  10  of  FIG. 2  is preferably used as a controller or joystick and the device  10 A of  FIG. 11  is preferably used as a wrist. 
     The device  10  of  FIG. 1  has moveable portion MP with a main axis  12  and is provided with an end point P 1 , which in the illustrated arrangement has a lever  14  rigidly connected thereto for movement relative to a base B (equivalent to table  4  of  FIG. 1 ). 
     The first and second degrees of freedom (DoF) are each provided by identical mutually perpendicular six-bar pantograph  16  and  18 , respectively, which permit the end point P 1  (P 2 ) to be manipulated in a hemispheric motion (or if used as a wrist when manipulated move the end point P 1  to define a hemispherical motion) about a center point F (see  FIG. 3 ), fixed relative to the base B and the location of which will be described below. The links  16 L of the pantograph  16  are jointed together by shafts  16 S and ball bearings (not illustrated) and the links  18 L of the pantograph  18  are jointed together by shafts  18 S and ball bearings (not illustrated). 
     The base link  16 LB and  18 LB of the pantographs  16  and  18 , respectively are integral with their respective arms  20  and  22  which in turn are fixed to shafts  24  and  26  rotatably mounted on the base B on bearing pedestals  28  and  30 , respectively. 
     The center point F is the intersection of the axes  24 A and  26 A of the shafts  24  and  26  (See  FIG. 3 ) which are located in the same plane and as above indicated are mutually perpendicular to each other and the main axis  12 . The length of the arms  20  and  22  are identical so that the offsets a 1  and a 2  of the links  16 LB and  18 LB, respectively from their respective shaft axis  24 A and  26 A are identical. 
     Each of the shafts  24  and  26  is provided with its respective actuator A 1  and A 2  which may take the form of a grounded electric motor m 1  and m 2 , respectively, equipped with encoder e 1  and e 2 , respectively, that determine the position or angular orientation of the shaft  24  or  26  relative to a base position. The actuators A 1  and A 2  are each fixed relative to the base B by mounting arms  32  and  34 , respectively. 
     The sleeves  17  and  19  connect links  16 LS and  18 LS (links remote form the links  16 LB and  18 LB) of the pantographs  16  and  18  through suitable bearings as will be described below to the end point P 1  so that movement of the pantographs  16  and  18  are transmitted to the end point P 1  to move same about the center point F as described above. The links  16 LS and  18 LS provide essentially the same length offsets a 3  and a 4 , respectively from the main axis  12  of the haptic  10 . 
     The offsets a 1 , a 2 , a 3  and a 4  will normally all be of equal length and the lengths of the links between shafts will be set as in most conventional pantographs i.e. opposed links of equal length. 
     This assembly consisting of the two pantographs  16  and  18  provides for two degrees of freedom. Actuator A 1  turns and/or measures the turn of the pantograph  16  about the axis  24 A (see  FIG. 3 ) of the shaft  24  and thus turns (to apply force feedback to the operator when used as a Haptic or to manipulate the point P 1  when used as a wrist) and/or measures one of the first two degrees of freedom and causes the links  18 L to rotate on their respective shafts  18 S. The other of the first two DoF is measured and/or controlled by actuator A 2  applies the same turning or measuring operations to pantograph  18  as the Actuator A 1  that applies to the pantograph  16  i.e. turns and/or measures the turn of the pantograph  18  about the axis  26 A of the shaft  26  that causes links  16 L to rotate about the their shafts  16 S. It will be apparent that rotation of the pantographs  16  and/or  18  on their respective shafts  24  and  26  pivot the main axis  12  about the center point F ( FIG. 3 ) so that the end point P 1  is moveable to define a hemispherical motion about the center point F. It is also apparent that the first and second DoF are decoupled. 
     The third DoF provides a sliding motion along the main axis  12  which is also the radius of the hemisphere created by the first two degrees of freedom and which has its center at the center point F (see  FIG. 3 ). 
     The operating system for this degree of freedom (see  FIG. 4 ) includes an actuator A 3  that normally will include a direct drive electric motor m 3  and encoder e 3  that is connected to base B through flange (disk)  47 . An inner universal joint  40  has one side  40   a  coupled to shaft  42  [which forms part of the first inner element that includes the system  50  (first portion) and slider  74  (second portion) to be described below] and its other side  40   b  (second side) coupled directly to the shaft  44  (second inner element) of the actuator A 3  and its pivotal axis  40   c  aligned with and defining the center point F. The shaft  44  is mounted for rotation relative to the base B by suitable ball bearings or the like schematically represented by the flange (disk)  46  in  FIG. 4 . Shaft  44  can be connected to the shaft of the actuator A 3  preferably by a suitable coupling such as the one shown in as part  45  in  FIG. 9 . 
     A belt or cable drive system  50  (first portion) (see  FIGS. 4 and 5 ) drives or is driven by the pulley  52  fixed to shaft  42  and incorporates a plurality of guide pulleys  54  and a turn around pulley  56  that are arranged to insure the closed-loop cable  58  travels in a path having a significant portion of its travel substantially parallel to the axis  12 . 
     As shown in  FIG. 5  pulleys  54  are mounted on a first normally lower support  60  on which a second normally an upper support  62  for mounting the pulley  56  is preferably adjustably mounted via a connection schematically represented by the shaft  63  from the lower support  60 . The upper support  62  mounts the turn around pulley  56  to form the cable or belt runs  66  and  68  that are substantially parallel to and are moved by rotation of the pulley  52 ,  54  and  56  in a direction substantially parallel to the axis  12  as indicted by the arrow  70 . 
     As shown in  FIG. 6  the tension in the belt or cable  58  is adjusted by turning the shaft  64  which has an offset portion  65  on which the pulley  56  rotates and which provides an offset a 5  so that rotation of shaft  64  changes the position of the periphery of the pulley  56  relative to pulley  54  to thereby adjust the tension in the belt or cable  58 . The shaft  64  is locked into adjusted position by any suitable means in the illustrated arrangement. A setscrew, for example, may be provided in the lower portion of the holes  61  (see  FIG. 5 ) to engage and lock the shaft  64  on opposite sides of the pulley  56 . 
     The lower support  60  is mounted via a suitable decoupling bearing structure  72  on the axial end of shaft  42  remote from the universal joint  40  so that the shaft  42  rotates freely relative to the support  60 . 
     The support platform  60  and the rest of the cable drive system  50  may be prevented from rotation by any suitable means a preferred form of which is illustrated in  FIG. 7 . In the illustrated arrangement the support  62  is coupled to a lower portion  17   a  of the sleeve  17  by a tongue formed by a cross bar  17   b  on the sleeve  17  and a mating groove  62   a  provided on the support  62 . Also bolts (not shown) pass through holes (not shown) in the bar forming tongue  17   b  are threaded into the upper portions of the threaded holes  61  to firmly secure support  62  and sleeve  17  together. The bar  17   b  provides extend diagonally across the sleeve which is hollow and provides spaces  17   c  one on each side of the bar  17   b  (only one shown) that permits the struts  74   a  and  74   b  to be received therein so that the top end member  74   c  is moved up and down within the sleeve  17  as will be described below. 
     The slider  74  is made of several parts namely a pair of opposed struts  74   a  and  74   b  connected at their opposite ends by end members  74   c  and  74   d . When the device is assembled, the bar  17   b  slides across the slider  74  between the struts  74   a  and  74   b  on the side of the top end member  74   c  remote from the shaft  76  and then connected to the sleeve  17  as shown. 
     A slider  74  (second portion) is fixed to one side of the cable route  58  at point indicated as point Y ( FIG. 4 ) and is connected to a ball spline and shaft  76  system through a ball bearing  78  ( FIG. 4 ). The ball bearing  78  decouples the rotational motion of the ball spline shaft  76  from the slider  74 . The ball spline shaft  76  as is well known is a linear motion system, in that balls accommodated in the spline nut  75  transmit torque while permitting linear or axial movement on precision raceways on a spline shaft. 
     The other side of the cable  58  passes through slider  74  without any contact with the slider  74 . 
     The cable drive system  50  particularly the cable  58  converts the rotational motion of the actuator A 3  and the inner universal joint  40  into the sliding one of the slider  74 . The axis of the sliding motion of the slider  74  is concentric with the main axis  12  of the device ( FIGS. 2 ,  3  and  4 ). The universal joint  40  allows the third degree of freedom to idly follow the first two DoF provided by the pantographs  16  and  18  while transmitting rotational motion of its own degree of freedom. 
     The end point P 1  is in the illustrated arrangement is at the end of shaft  76  remote from the base B and may be connected directly to other elements such as handle  14  to achieve the desired purpose. 
     The fourth subassembly illustrated in  FIGS. 2 ,  8  and  9  is optional and is only provided if the system is to have 4 DoF i.e. if rotational motion of the end point P 1  is to be provided. The axis of rotation is concentric with the main axis  12 , which is concentric with the shaft  76  and  42  and with the sleeves  17  and  19 . 
     Referring to  FIG. 8  this fourth DoF is provided by an outside universal joint  90  concentric with the inner universal joint  40  (see  FIG. 9 ) so its pivot point is also aligned with the center point F. One or a first side  90   a  of the outer universal joint  90  is connected to a first outside element  94  that as will be described below is connected to the shaft  76  to apply rotational forces thereto and thereby to the end point P 1 . A second side  90   b  of the outside universal joint  90  is mounted on the base B via a suitable rotatable pedestal  98  that rotates on the base B via bearings mounted on flange (disk)  46 . A pulley  100  of the belt or cable drive system  102  is fixed to rotate with the pedestal  98  to drive or be driven by the universal  90  as will be described below. The outer universal  90  has a hollow ring  90   c  to which the sides  90   a  and  90   b  are pivotably connected in the conventional manner to provide that hollow interior in which the inner universal  40  is received. 
     The belt or cable drive system  102  further includes a belt or cable  104  that drivingly connects the pulley  100  to the pulley  106  of the Actuator A 4 . The actuator A 4  will normally include a grounded electric motor m 4  and encoder e 4 , to drive and/or monitor the movement of the element  94 . The actuator is fixed to the base B through flange  107 . A preferred form of drive for fourth degree of freedom is illustrated in  FIGS. 8 and 9  and represents rotation on an axis of rotation concentric with the main axis  12 . 
     The power train for this subassembly consists of belt or cable drive system  102  described above and the second cable drive  400 . The second cable drive  400  consists of an lower pulley  420  embedded in the upper part of connecting tube  94 , two guiding pulleys  421 , two tension adjuster mechanisms  422 , closed loop cable  423  and an upper pulley  424  which is connected to and drives the spline nut  75  about the axis  12 . The upper pulley is mounted on the sleeve  17  via ball bearings (not shown) that permit the pulley  424  is, mounted on the sleeve  17  via decoupling ball bearings (not shown) that permit the pulley  424  to freely rotate on the axis  12  relative to the sleeve  17 . The guiding  421  and the tension adjuster pulley  422  are mounted on sleeve  17  of link  16 LS block by block  425 . The tension adjuster mechanism consists of pulleys  422   a , links  422   b  and tightening nuts  422   c . By turning and tightening the link  422   b  and the nut  422   c , respectively, the user is able to adjust the cable tension. Cable  423  transmits motion from lower pulley  420  to upper one  424 . The ball spline nut  75  permits relative axially movement between the pulley  424  and the shaft  76  while transmitting rotational movement there between. The ball spline nut  75  is fixed to upper pulley  424 . 
     The connecting tube or housing  94  is jointed to sleeve  17  of link  16 LS of the pantograph  16  through a ball bearing (not shown) that decouples the rotational motion of connecting tube  94  from link  16 LS. 
     In some cases it may be desirable to have a sleeve P 2  or the like that encircles the controller  10  and is connected to the handle  14  to provided an auxiliary end point P 2  which may be grasped by the user by either one of or both hands to facilitate manipulation of the haptic  10 . This construction allows the user to hold the handle in two places i.e. one hand on top at P 1  and another encircling the housing  94  at P 2 . In order to maneuver the housing  94  at P 1 , the operator must mainly move her/his elbow and upper arm. Maneuvering the housing  94  at P 2 , on the other hand, requires the movement of the hand about the wrist only. Such an arrangement is shown in  FIG. 10 . 
     In the illustrated version the handle  14  has been shown located in the 90° segment between the pantographs  16  and  18  for convenience so it is visible, it will normally be on the opposite side i.e. in the 270° segment between the pantographs  16  and  18  to provide 270° of free movement. It will be apparent that if 360° movement is desired the handle  14  may be eliminated. 
     Turning to  FIG. 11  wherein the operation of the device is illustrated schematically the centerline CL indicates the datum centerline of the device and assuming the device is oriented vertically this line CL will extend vertically from the center point F. The axis  12  is manipulated so that the plane PL containing the point P 1  extends at any suitable selected angle β 1  measured from the CL about X axis (assuming CL is the Z axis) and the point P 1  is at second selected angle β 2  measured from the Z axis of CL on plane PL about the Y axis. These angles β 1  and β 2  are determined by the pantographs that have been pivoted from their respective datum positions which for the purpose of this description is the location when the centerlines CL and  12  coincide. In effect rotation of the pantographs  16  and  17  on their respective axes  24 A and  26 A result in mutually perpendicular displacements of the centerline  12  relative to centerline CL as indicated by the arrows  450  and  452 . Thus, movement of the pantographs  16  and  18  about their respective axes  24 A and  26 A results in adjusting the size of angle β 1  and β 2  and thereby the positioning of point P 1  relative to the centerline or axis CL. 
     The third degree of freedom moves the end point P 1  axially along the axis  12  as indicated by the arrow  456  in  FIG. 11  and the fourth degree of freedom rotates the end point P 1  around the axis  12  as indicated by the arrow  458 . 
     The above-described combination preferably will be used as a haptic controller i.e. a joystick with force reflecting capability. It may be used to control the motion of, and reflect the forces from a remote wrist performing selected operations such as palpation or ultrasound diagnosis. 
     Preferred Form of Wrist 
     Similar parts of the controller  10  described above to those equivalent parts of the wrist  10 A are called by similar names in the following description of the wrist  10 A which as above indicated may also be used as a controller or haptic. 
     Referring to  FIG. 12 , the device  10 A which may function as either a haptic or controller or a wrist and which preferably is used as a wrist in the present invention is provided with moveable portion or section MPA having a main centerline  212  and end point or probe PA that is being manipulated. This probe PA is primarily manipulated about a center point or a center-of-motion point FCM (see  FIG. 14 ). The probe PA may also be manipulated as will be described below for axial and or rotational motion relative to the main centerline  212  of the main or moveable section MPA in which the operating modules (described below) are to be amounted. This moveable section MPA is oriented as will be described below by a pair of pantographs  216  and  218  which operate or are operated to orient the section MPA particularly the probe PA in a manner similar to the operation of the pantographs  16  and  18  in the positioning of the end point P 1 . 
     A pair of six-bar pantographs  216  and  218  similar to the pantographs  16  and  18  of the above-described controller are mounted on a frame  220  suspended from the base BA defines the first two DoF of the probe PA (which is the wrists equivalent to the end point P 1  and is manipulated in a manner similar or equivalent to the movements of the end point P 1  of the haptic or controller  10  described above). The frame in the illustrated arrangement (see  FIGS. 13 and 17 ) is formed by a pair of pillars  222  and  224  to which is attached a substantially semi circular bar  226  on which the turning axels  228  and  230  (see  FIG. 14 ) of the pantographs  216  and  218  are mounted. 
     The axes  232  and  234  of the axles  228  and  230  are positioned in their corresponding axial planes 90 degrees apart. These axes  232  and  234  are set at the same selected angel a relative to the main axis  212  so that they are in effect in the same cone relative to the datum centerline CL 1  of the moveable section MPA which is equivalent to the centerline CL of the device  10  described above and is thus coaxial with the axis  212  when the axis  212  is in neutral position—in the illustrated arrangement when the axis  12  is substantially vertical. 
     The point of intersection of projections of axes  232  and  234  with each other and with main axis  212  (and with the centerline CL 1 ) defines the location of the center-of-motion point FCM. 
     The pantographs  216  and  218  operate in the same manner as the pantographs  16  and  18  described above in that as they are rotated with their respective shafts  228  and  230  (the plain of each pantograph is located in the plain of their respective shafts  228  and  230 ) to define a hemispherical motion of the point PA (which may for example indicate the surface of an ultrasound or palpation probe) about a remote center-of-motion (FCM) (see  FIGS. 14 ,  15  and  16 ). In the  FIG. 14  position the center-of-motion point FCM which is fixed relative to the base BA is shown aligned with the extreme free end PAF of the probe PA. It will be apparent that the axial extension of the probe relative to the moveable section MPA as will be described below and as schematically indicted in  FIG. 14  by the arrow  235  will change the operation or movement of the probe PA for a given change in movement of the pantographs  216  and  218 . It is preferred to position the center-of-motion point FCM so that axial movement of the probe PA may position the free end PAF on opposite sides of the center-of-motion point FCM. 
     As above indicated the rotatable shafts  228  and  230  are each is fixed to and positioned in fixed relation to the base BA via the frame  220 . Mounted on the base BA are a pair of actuators A 5  and A 6  each of which may include its motor m 5  or m 6  and suitable encoders e 5  and e 6  that drives (or is driven by) and measures the rotation of its respective pantograph  216  and  218 , respectively, via their respective shafts  228  and  230 . 
     The motors m 5  or m 6  may have a gearbox for torque increase or speed reduction if desires and may also be directly coupled to shaft  228  and  230 , respectively, in applications whereby motor closeness to the FCM is not of concern, however it is preferred to couple each of the motors m 5  or m 6  to its respective shaft  228  and  230  via the belt or cable drives  236  or  238 , respectively. 
     The cable drive  236  and  238  are essentially the same except one  236  connects actuator A 5  with shaft  228  and the other  238  connects the actuator A 6  to the shaft  230 . Thus only the drive  238  will be described with reference to  FIGS. 13 ,  14 ,  16  and  17  it being understood that the drive  236  is essentially the same. 
     As shown the shaft  240  (see  FIG. 16 ) of the motor m 6  has a pulley  242  mounted thereon and drives a cable  244  that passes over and is guided by suitable guide pulleys  246  some of which may also function as tensioners to tension the cable  244  and drives pulley  248 . The pulley  248  has a companion pulley  250  fixed for rotation therewith and this pulley  250  drives a second cable  252  that drives the shaft  230  via pulley  254 . A suitable tensioning pulley  256  may be provided, if desired. 
     As indicated the first degree of freedom is generated by motor m 5  and the cable drive that turns the pantograph  216  about the axis  232  of the shaft  228 . The drive m 6  for second degree of freedom may but need not be idle when the first is operated but when activated rotates the second pantograph  218  with its shaft  230  i.e. about its axis  234 . 
     A view of pantograph  218  is shown is  FIG. 15 . The lengths of the links in each pantograph  216  and  218  comply with the conventional length conditions used in most pantographs. 
     The first and second pantographs  216  and  218  as above indicated are located in two perpendicular planes. The pantographs  216  and  218  each connect to the device via their respective sleeves  260  and  262  i.e. the pantograph  218  has its link  264  remote from the shaft  230  connected to the sleeve  260  (see  FIGS. 14 ,  15  and  16 ) and similarly the pantograph  216  has its link  266  remote from its shaft  228  fixed to the sleeve  262 . The sleeves  260  and  262  are concentric with and may rotate relative to each other about the axis  212 . Sleeves  260  and  262  are joined together via suitable ball bearings. 
     These two degrees defined by the pantographs  216  and  218  are decoupled. 
     The third DoF of the end point PA is provided by a shaft system  270  (see  FIG. 18 ) formed by three shafts interconnected by a pair of inner universal joints namely a first inner universal  278  inter connecting shafts  276  and  284  and a second inner universal joint  280  interconnecting the shafts  272  and  282  (which is part of shaft  284 ). The shaft  272  is driven by actuator A 7  that normally will include a motor m 7  and an encoder e 7 . The shaft  272  is in effect the motor shaft of the motor m 7  and the shaft  284  is made of an inner ball spline shaft  282  and outer ball spline nut  283  coupled together to permit relative axial movement while prohibiting relative rotational movement. Ball spline nut  283  is fixed to shaft  284  and thus connected to the first inner universal joint  278 . 
     The shaft  276  coupled to the other side of the first inside universal joint is an output shaft that couples to the various modules (described below) that may interchangeably be received in the sleeves  260  and  262  of the mobile section MPA to drive same if required. The fourth DoF is provided by the mechanism shown in  FIGS. 19 , to  22 . This fourth DoF is a rotation about the radius of the hemisphere created by the first two degrees of freedom and which is coaxial with the main axis  212  i.e. the rotational axis of the sleeves  260  and  262  is main axis  212 . The roll or rotation motion is provided by the actuator A 8  that normally includes a grounded electric motor m 8  and an encoder e 8  The rotational motion from the electric motor m 8  is transmitted through a first cable or belt drive  290  composed of pulley  292 , cable or belt  294  and pulley  296  that is attached to one side  300   b  of a second outside universal joint  300  that is concentric with the second inside universal joint  280 . The other side  300   a  of universal joint  300  is coupled to an inner shaft  302  that telescopes within the concentric outer shaft  304  and these two shafts  302  and  304  are splined together by spline  306  and mating element  305  secured to shaft  304  (see  FIGS. 20 and 22 ) so that the shafts  302  and  304  rotate together but permit relative axial movement there between in the same manner as the shafts  282  and  284 .  300   a  and  300   b  are connected together by ring  300   c , which also provides enough space to receive the inside universal joint  280 . 
     The outside shaft  304  at its end remote from the universal joint  300  is fixed to one side  310   b  of a first outside universal joint  310  which is concentric with the first inside universal joint  278 . The other side  310   a  of the universal joint  310 ,  310   a  is connected to  310   b  by ring  310   c  from one end, and to a pulley  314 , from other end, to form the driving pulley for a second cable or belt drive system  316  wherein a belt or cable  318  passes over a plurality of properly positioned idle or guiding rollers  320  and a driven pulley  322  mounted on the sleeve  260  of the moveable section MPA for rotation about the axis  212  and fixed to a rotably driven module element to drive the module as will be described below. Pulley  314  is connected by a bearing to cup  259 , which is in turn rigidly connected to  260 . 
     A suitable cable or belt tensioning system  324  is provided for the belt or cable  318  and is formed by a pulley  324   a  mounted on an arm  324   b  whose position is adjustable to change the position of pulley  324   a  by means of nuts  324   c.    
     The guide rollers  320  and the tensioning systems  324  of the drive system  316  are mounted on the sleeve  260  of the pantograph through a series of modular blocks  340 ,  342  and  344  ( FIGS. 19 and 20 ). 
     The first cable drive  290 , drives the second outside universal joint  300  which in turn drives the first outside universal  310  via the telescoping shafts  302  and  304  interconnected by the spline  306  and the universal  310  that drives the cable system  316  thereby transmitting torque from a fixed rotation source A 8  to a moving joint in space in any orientation (see  FIGS. 19 , and  20 ). This allows a module (described below) mounted in the sleeves  260  and  262  of the moveable portion or section MPA to be rotatably driven and to idly follow the movement of the moveable portion MPA by the first two DoF for the moveable section MPA so that torques is transmitted to drive the fourth DoF of the wrist  10 A. 
       FIG. 21  shows the relationship of the actuators A 7  and A 8  and their respective driving relationships with the second inside universal  280  and second outside universal  300 , respectively and the concentric relationship of the two second universals  280  and  300  that are mounted with respect to each other by a ball bearing. As above indicated the two first universals namely first inside universal  278  and first outside universal  310  have a similar concentric relationship to that shown in  FIG. 21  for the second inside  280  and second outside  300  universals and above described for the inside and outside universals  40  and  90  of the device  10  described above. 
     The wrist  10 A may include more than one module designed so that the modules can be easily substituted for one another i.e. quickly attached and/or detached in the sleeves  260  and/or  262  of the moveable section MPA. 
     The wrist  10 A in the illustrated embodiments is provided with two interchangeable modules  500  and  600  each of which may be quickly attached and detached (see  FIGS. 23 to 26 ). 
     The first module  500  has two degrees of freedom ( FIGS. 23 and 24 ). This module  500  transmits the rotation of pulley  314  to the working probe  532  forming the end point PA. It also converts motion of the fourth degree of freedom i.e. the rotation of shaft  276  into the sliding motion of the working probe  532 . 
     The module  500  has an outside housing  526  that is received in and detachably mounted in the moveable section MPA in any suitable manner. In the arrangement illustrated in  FIG. 24  a retractable coupling pin pins the module in position and functions to prevent rotation of a slider  528  as will be described below. 
     The shaft  276  is coupled to a ball screw drive shaft  525  of the module  500  via a self-aligning coupling  502  and drives a ball screw&#39;s nut  527  fixed to a slider  528  (see  FIG. 24 ). Linear guides  529  are fixed to end support  533 , and prevent rotation of the nut  527  with the shaft  525  while permitting relative axial sliding movement between the slider  528  and the end support  533 . The end support  533  is fixed to sleeve  260  of the pantograph  218  by a coupling pin schematically indicated at  506  to prevent rotation of the end support  533  and thereby through guides  529  prevent rotation of the slider  528 . The ball screw drive shaft  525  is mounted on end support  533  by a ball bearings (not shown). The linear guides  529  are connected to slider  528  by two linear ball bushing (not illustrated). 
     Slider  528  is mounted on connector  530  via a decoupling ball bearing (not shown). Thereby to decouple the rotating motion of connector  530  imparted by the drive  316  from sliding motion of the slider  528  so that the module can achieve three modes of motion (rotational, sliding and spiral as needed). 
     The connector  530  also connects the working probe  532  with a ball spline nut  531  that prevents relative rotational movement of the probe PA and the housing  526  while permitting relative axial movement parallel to axis  212  there between. The housing  526  is connected to pulley  322  by coupling pin schematically indicated at  508  and receives it rotary motion from pulley  322  driven via drive  316  as above described. Obviously the rotary motion imparted to the housing  526  is transferred to the probe PA by the spline nut  531 . 
     Probe  532  is preferably attached to the connector  530  through an off-the-shelf six axes force/torque sensor (not shown). 
     When the module  500  is in operative position (see  FIG. 24 ), ball screw&#39;s shaft  525  is connected to the shaft  276  by off-the-shelf self aligning coupling  502  and the housing  526  of the module  500  (or  600 ) is mounted within the outer housing formed by sleeve  260  on suitable bearings (not shown) and pinned in place by pin  506  (and  508 ) as described above. 
     This module in combination with the four degrees of freedom allows the wrist to orient and palpate. 
     The second module  600  (see  FIGS. 25 and 26 ) converts the rotary motion of the shaft  276  into a sliding motion of the probe  638  (probe PA) along the radius of the hemisphere created by the action of the pantographs  216  and  218  to provide a wrist with three degrees of freedom. 
     This module  600  has housing  640  in which the inner elements of the module  600  are contained. 
     A drive shaft or ball screw  634  of this module  600  is coupled to the shaft  276  via a self aligning coupling  602  (see  FIG. 26  similar to the coupling  502  described above) and rotation of the ball screw shaft  634 , tends to rotate nut  637 , which is connected rigidly to slider  642  and which in turn is connected via extension  644  to the probing device  638  forming the end point PA. Slider  642  is restrained from rotation by the linear guides  636  (two shown) connected to the slider  642  by sets of linear ball bushings (not shown) that permit relative axial movement between the guides  636  and the slider  642 . Therefore, rotation of the ball screw shaft  634  causes the nut  637  and slider  642  moves along the ball screw  634 . 
     The linear guides  536  are rigidly connected to plates  635  and  639 , which are in turn fixed to the housing  640 . The housing  640  is connected to sleeve  260  by coupling pin  604 . This module does not receive any motion from pulley  322 . 
     In combination with the first three degrees of freedom, this module is able to perform the palpation action in any orientation and reports on all arising forces from palpation.  FIG. 27  schematically indicates the action of the wrist  10 A. As illustrated the angle θ 1  and θ 2  (which are essentially equivalent to the angles β 1  and β 2  of the embodiment of  FIGS. 2 to 11 ) between the datum centerline CL 1  for the moveable section MPA and the actual central or main axis  212  at the center of movement FCM measured in the planes relative to the X and Y axes, respectively, in the same manner as angles β 1  and β 2 . These angles θ 1  and θ 2  are determined by the action of the two pantographs  216  and  218  in the same manner as the pantographs  16  and  18  determined the angles β 1  and β 2  as described above for the haptic device  10 . The end point PA may be moved by the pantographs  216  and  218  in two mutually perpendicular directions as indicated by the arrows  700  and  702  and depending on the module used i.e. module  500  or  600  may be moved both axially as indicated by the arrow  704  and rotated around the axis  212  as indicated by the arrow  706  when the module  500  is used, or when the module  600  is used there is no movement as schematically indicated by the arrow  706 . 
     The device  10 A may be set so that axial travel of the probe PA along the axis  212  between the points A and B as indicated by the dimension D may set so that one extremity of travel point A is on one side of the center FCM and the opposite extremity point B is on the opposite side of center FCM along the axis  212 . It will be apparent that movement of the end point PA moves on a hemisphere based on the position of the end point PA relative to the point FCM and will have having a radius measure along axis  212  from point PA to the point FCM. When the point PA is to the left of the point FCM in  FIG. 27  the point PA moves in a convex pattern, but when PA is on the opposite side of the point FCM it moves in a concave pattern when the pantographs  216  and  218  are manipulated. 
     If desired the location of the center FCM may be made adjustable by having the lengths of the links of the pantographs  216  and  218  connecting the pantographs to the MPA to be axially adjustable. 
     Having described the invention, modifications will be evident to those skilled in the art without departing from the scope of the invention as defined in the appended claims.