Patent Publication Number: US-2006009891-A1

Title: Manipulable input device with adjustable magnetorhelogical motion damper

Description:
TECHNICAL FIELD OF THE INVENTION  
      This invention relates to input devices for providing control inputs to a machine, and more particularly to providing damping of movement of such input devices to provide a desired tactile feel for a user of the control device.  
     BACKGROUND OF THE INVENTION  
      It is common practice to utilize an input device, such as a keypad, joystick, a hand or thumb wheel, foot pedal, or lever, for communicating an input command to a machine, such as a computer, video game, a medical device, a robotic system, or other types of control systems.  
      It is also known to utilize some form of damping of the input, in such control devices, to provide a desired tactile feel or force feedback through the input device to the user. For example, U.S. Pat. No. 6,486,872, to Rosenberg, et al, discloses a method and apparatus for providing passive force feedback.  
      Prior input devices utilize a variety of types of damping devices, including hydraulic dampers using a magnetorheological (MR) working fluid, which has fluid properties that change when exposed to a magnetic flux. MR fluids contain minute ferromagnetic particles that align with one another when exposed to a magnetic flux. By causing the alignment of the ferromagnetic particles of the MR fluid to change, shear forces generated within the MR fluid, when the MR fluid is subjected to an external force, are altered in a manner that causes the apparent viscosity of the MR fluid to change. The operating characteristics of the damper are dependent upon the fluid properties of the MR working fluid. By controlling the level and orientation of magnetic flux applied to the MR fluid, the operating characteristics of the hydraulic damper can be altered to provide a desired level of damping.  
      Prior MR devices typically include a movable piston having one or more holes therein, for passage of the MR fluid. The movable piston also typically includes electrical coils for generating a magnetic flux in the holes of the movable piston, for causing the viscosity of the MR fluid to change as it travels through the holes in the piston.  
      The need to provide the movable piston, and to make the piston physically large enough so that it can include the holes and electrical coils, has caused prior damping devices using MR fluid to generally be relatively large, and not well suited to smaller sized input devices.  
      The present invention provides a method and apparatus, utilizing MR fluid, that is particularly suited for providing damping in smaller sized input devices, but can also be used in larger sized input devices to provide improved functionality, and other advantages that are not provided by prior input devices.  
     SUMMARY OF THE INVENTION  
      The present invention provides an improved method and apparatus for damping an input device, through the use of a damping element adapted for attachment between a support, and an input element of the input device, which is configured for receiving an input through manipulation of the input element by a user. The input generates a movement of the input element. The damping element includes a cavity forming element and a magnetizable element. The cavity forming element defines one or more cavities containing a magnetorheological (MR) fluid. The magnetizable element is disposed at a position adjacent the MR fluid for impressing a magnetic field on the MR fluid, to thereby alter the viscosity of the MR fluid and damp the movement of the input element generated by the input.  
      In contrast to prior hydraulic dampers utilizing MR fluid, the magnetizable element is not required to be located in holes allowing passage of the MR fluid, and a movable piston is not necessarily required in all embodiments of the present invention.  
      In one form of the invention, the cavity forming element comprises a compliant member operatively connected between the input element and the support. The compliant member is formed from a resilient material, and defines at least one of the one or more cavities containing the magnetorheological fluid. The compliant member has a stiffness that is defined by the structure of the compliant member and the material properties of the resilient material and the MR fluid. Application of the magnetic field to the MR fluid changes the stiffness of the compliant member by changing the flid properties of the MR fluid in one or more of the one or more cavities of the compliant member.  
      The compliant member may include a porous segment forming at least one of the one or more cavities containing the MR fluid. The porous segment may be sponge-like, having a plurality of cells defining a plurality of the one or more cavities containing the MR fluid. The porous segment may also be fibrous, having a plurality of fibers forming a plurality of spaces therebetween defining a plurality of the one or more cavities containing the MR fluid. The compliant member may also be formed of a resilient material having veins or micro-tubes therein, oriented in an ordered array or randomly, in various embodiments of the invention, with the veins or micro-tubes forming the one or more cavities for the MR fluid.  
      In another form of the invention, the damping element includes a damper housing having a bore defining an axis, and a movable member disposed within the bore. The movable element is operatively attached to the input element for movement thereby with respect to the axis. The cavity forming element may include the housing, with the bore in the housing defining the cavity, and the cavity defining the axis. Application of magnetic flux, to the MR fluid in the cavity, increases resistance to movement of the movable element in the cavity. The movable element may further include a hole therein for passage of the MR fluid therethrough, with application of magnetic flux to the MR fluid in the cavity causing an increase in resistance to the passage of MR fluid through the hole in the movable element.  
      The movable element may be rotatable about the axis and may include one or more paddles extending therefrom. At least one of the paddles extending from the movable element may further include a hole therein for passage of the MR fluid therethrough, and wherein application of magnetic flux to the MR fluid in the cavity increases resistance to the passage of MR fluid through the hole in the at least one paddle of the movable element.  
      In some forms of the invention, a compliant element is disposed within the bore and operatively connected between the movable element and the housing, with the compliant element including a porous segment having one of the one or more cavities therein containing the magnetorheological fluid, with the compliant member further having a stiffness. Application of the magnetic field to the MR fluid changes the stiffness of the compliant member. The porous segment may be sponge-like, or fibrous. The compliant member may be fixedly attached to the housing and slidably contact the movable element. Conversely, the compliant member may be fixedly attached to the movable element and slidably contact the housing.  
      The invention may also take the form of a method for damping movement of an input element of an input device with respect to a support of the input device, utilizing a damping element as disclosed herein. The method may include, connecting the input element to the support with a damping element having a compliant member, and also having a compliant member defining one or more cavities containing an MR fluid. The method may further include additional steps such as: impressing a magnetic flux on the MR fluid; controlling the intensity of the magnetic flux impressed upon the MR fluid; setting a threshold value of stiffness of the compliant member by impressing a threshold level of magnetic flux intensity on the MR fluid; and/or controlling the stiffness of the compliant member by altering the threshold level of magnetic flux intensity.  
      The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of exemplary embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1 and 2  are schematic representations of exemplary embodiments of control systems, including input devices and MR damping elements, according to the invention, for receiving a linear input.  
       FIG. 3  is a schematic representation of an exemplary embodiment of a control system, including a rotary input device and MR damping element, according to the invention, for receiving a rotary input.  
       FIGS. 4   a - 4   f  are cross sectional views of six exemplary embodiments of a linear input device, according to the invention.  
       FIGS. 5 and 6  are enlarged representations of two exemplary embodiments of a compliant member according to the invention, formed from a porous sponge-like, or fibrous material, respectively.  
       FIGS. 7 and 8 , respectively, are enlarged cross sectional views of MR damping elements, according to the invention, having a linearly movable member disposed in a bore containing MR fluid.  
       FIGS. 9 and 10  are side and end cross sectional views of a first exemplary embodiment of a rotary damping element, according to the invention.  
       FIGS. 11-13  are side cross sectional views of alternate exemplary embodiments of rotary damping elements, according to the invention.  
       FIGS. 14   a - 14   c  show several alternate embodiments of a movable element for a rotary damper, according to the invention, of the type shown in  FIGS. 9 and 10 .  
       FIGS. 15   a - 15   e  show several alternate embodiments of a movable element for a rotary damper, according to the invention, of the type shown in  FIGS. 11-13 .  
       FIGS. 16   a - 18   b  show alternate exemplary embodiments of a linear input device, according to the invention. 
    
    
      Throughout the drawings and the following descriptions of exemplary embodiments, like elements are identified with the same reference numerals.  
     DETAILED DESCRIPTION  
       FIGS. 1-3  show three exemplary embodiments of a control system  10   a ,  10   b ,  10   c , each including a controlled device  12 , a controller  14 , a sensor  16 , and an exemplary embodiment of the invention in the form of an input device  18 , including a support  20 , an input element  22 , and a damping element  24 .  
      In each of the exemplary control systems  10   a ,  10   b ,  10   c , the input element  22  is configured for receiving an input, through manipulation of the input element  22  by a user, for generating a movement of the input element  22 . As described in more detail below, an input device  18  and damping device  24  of the invention can be configured for operation with inputs that are linear, rotary, a combination of linear and rotary, or applied obliquely to the input element  22 . In the input devices  18  of  FIGS. 1 and 2 , the input is linearly directed, as indicated by arrows  26 , along an axis  30  of the input element  22 . In the input device  18  of  FIG. 3 , the input may be directed either linearly, as shown by arrow  26 , or be a rotating input, as shown by arrow  28 .  
      The sensor  16  is operatively connected for detecting an application of the input  26 ,  28  to the input element  22 , and communicating an input signal indicative of the input  26 ,  28  to the controller  14 . The controller  14  is operatively connected between the sensor  16  and the controlled device  12 , and generates a control signal, which is communicated to the controlled device  12 , for controlling the controlled device  12  in a predetermined manner as a function of the input  26 ,  28 . The damping element  18  resists movement of the input element  22 , in response to the input  26 ,  28 .  
      In the embodiments of the control systems  10   a ,  10   b ,  10   c  shown in  FIGS. 1-3 , the controller  14  is also operatively connected to receive a feedback signal from the controlled device  12 , but it will be understood, by those having skill in the art, that in other embodiments of the invention there may be no feedback signal and the controller will operate the controlled device  12  in an open-loop fashion. In the embodiments of the control systems  10   b ,  10   c  shown in  FIGS. 2 and 3 , the controller  14  is also operatively connected to the damping element  18 , for controlling the level of damping applied to the input element  22 .  
      In each of the exemplary embodiments described herein, the damping element  24  is attached between the support  20  and the input element  22 . The damping element  24  in all embodiments includes a cavity forming element  25  defining one or more cavities  27  containing a quantity of magnetorheological (MR) fluid  32 , and includes a magnetizable element  34  disposed at a position adjacent the MR fluid  32 , for impressing a magnetic field on the MR fluid  32 , to thereby damp the movement of the input element  22  generated by the input ( 26  or  28 ).  
      The input device  18  and damping element  24  of the invention, may take many forms, some examples of which are described below, in conjunction with the accompanying drawing figures.  
      In the embodiment of the damping element  24  shown in  FIG. 1 , the magnetizable element  34  is a permanent magnet  36 , and the damping element  24  further includes a positioning apparatus  38  for adjusting the position of the permanent magnet  36  adjacent to the MR fluid  32  to a desired position adjacent the MR fluid  32 . The positioning apparatus may be a set screw, or any other appropriate mechanism known in the art, which may be adjusted by hand or with a tool to alter the position of the permanent magnet  36  with respect to the MR fluid  32 , to achieve a desired constant value of damping. This arrangement allows for the touch responsiveness of the input device  18  to be tailored to a particular user or control system application.  
      In the embodiments of the damping element  24  shown in  FIGS. 2 and 3 , the magnetizable element  34  is an electromagnet  40  for generating the magnetic flux, and the damping element  24  further comprises a magnetic flux controller  42  for adjusting the magnetic flux generated by the electromagnet  40  to a desired magnetic flux.  
      Although the exemplary embodiments of the control systems  10   a ,  10   b ,  10   c  show the sensor  16 , controller  14 , and electromagnet controller  42  schematically as separate components, they may be combined into one another, or divided differently than illustrated in  FIGS. 1-3 , in other embodiments of the invention.  
       FIGS. 4   a - 4   f  show several exemplary embodiments of input devices  18 , according to the invention, in the form of push buttons, or keys for a keypad, for receiving a linear input  26 . The input devices  18  of  FIGS. 4   a - 4   f  each include damping elements  24  in which the cavity forming element  25  includes a compliant member  44  operatively connected between the input element  22  and the support  20 , and defining at least one cavity  27  containing the MR fluid  32 . The compliant member  44  is formed of a material, such as such as silicone rubber, natural rubber, or any other suitable material that is pliable, bendable, resilient, and having a stiffness.  
      Each of the input devices  18  of  FIGS. 4   a - 4   f  also includes a contact  43  that interacts with a sensor (not shown) to provide a signal when the linear input  26  is applied to the input element  22  (i.e. push-button or key).  
      In the exemplary input devices  18  of  FIGS. 4   a - 4   e , the compliant members  44  take the form of generally conically shaped skirts connecting the input element  22  to the support  20 . In each of these embodiments, a portion of the compliant member  44  functions as the cavity forming element  25 , and defines at least one internal cavity  27  containing the MR fluid  32 .  
      In some embodiments, the cavity forming element  25  may be impregnated with MR fluid, as shown in  FIG. 4   e . In other embodiments, the cavity forming element  25  may define a single cavity  27 , or include a porous segment  46 , as shown in  FIGS. 5 and 6 , forming a plurality of cavities  27  containing the MR fluid  32 . The porous segment  46  may be sponge-like, as shown in  FIG. 5 , and have a plurality of cells  48  defining a plurality of cavities  27  containing the MR fluid  32 . Alternatively, the porous segment  46  may be fibrous and have a plurality of fibers  50  forming a plurality of interstitial spaces  52  therebetween, defining a plurality of cavities  27  containing the MR fluid  32 .  
      The input device  18  shown in  FIG. 4   f  also includes a conical skirt  54  of compliant material, but the cavity forming element  25  takes the form of a compliant button  56  extending from the contact  43  to bear against a surface below the support  20 .  
      In each of the input devices  18  of  FIGS. 4   a - 4   f , the magenetizable element includes an electrical coil  58  that is positioned adjacent the MR fluid  32  and operatively connected, via a circuit  60 , to a source of electrical current (not shown), for impressing a magnetic field on the MR fluid  32 . The circuit  60  may take any know form including wires, a circuit board or a flex circuit. In the embodiments of the input devices  18  shown in  FIGS. 4   a ,  4   b , and  4   e , the electrical coil  58  is attached to the support  20 . In the embodiments of  FIGS. 4   c ,  4   d , and  4   f , the electrical coil  58  is attached to the contact  43 . In the embodiment shown in  FIG. 4   d , the magnetizable element also includes a permanent magnet  62  disposed in the contact  43 .  
      By controlling the level of electrical current applied to the electrical coil  58 , the viscosity of the MR fluid  32  in the cavities  27  of the compliant members  25  of the input devices  18  shown in  FIGS. 4   a - 4   f  can be changed and controlled. When the viscosity of the MR fluid  27  in the compliant members  25  is changed, the stiffness of the compliant members  25  is also changed a corresponding amount, to thereby damp the movement of the input element  22  generated by the input  26 , for adjusting the tactile feel at the input element  22 .  
       FIGS. 7-13  show exemplary embodiments of damping elements  24 , according to the invention, in which the damping elements  24  include a damper housing  64  including a bore  66  defining an axis  68 , and a movable member  70  disposed within the bore  66  and adapted for operative attached to an input element (not shown) for movement thereby with respect to the axis  68 . The housing  64  functions as the cavity forming element and the bore  66  in the housing defines the cavity  27 , with the cavity defining the axis  68 . Each of these embodiments also includes an electrical coil  58 , for applying magnetic flux to the MR fluid  32  in the cavity  27  to control the viscosity of the MR fluid, and the amount of damping applied through resistance to movement of the movable element  70  in the cavity.  
       FIGS. 7 and 8  show damping elements  24 , for damping linear movement of the movable element  70  along the axis  68 , in response to an input  26 .  
      In the embodiment of  FIG. 7 , the movable element  70  includes a hole  72  therein for passage of the MR fluid  32  therethrough, and wherein application of magnetic flux to the MR fluid  32  in the cavity  27  increases resistance to the passage of MR fluid  32  through the hole  72  in the movable element  70 . In other embodiments of the invention, the hole  72  in the movable element  70 , of a damping element  24  of the type shown in  FIG. 7 , can be eliminated, and clearance provided between the movable element  70  and the bore  66  to force the MR fluid  32  to flow through the annular space formed by the clearance between the movable element  70  and the bore  6 . In other embodiments, the movable element  70  may be take the form of a compliant member, formed from a porous material, that is sponge-like, or fibrous, as discussed above in relation to  FIGS. 5 and 6 .  
      In the embodiment of  FIG. 8 , a compliant element  44  is disposed within the bore  66  of the damping element  24 , and operatively connected between the movable element  70  and the housing  64 , with the compliant element  44  including a porous segment  46  having one of the one or more cavities  27  therein containing the MR fluid  32 . Application of a magnetic field from the coil  58  to the MR fluid  32  changes the stiffness of the compliant member  25 , to thereby change the damping provided. The porous segment  46  of the compliant member  44  may be sponge-like, or fibrous, as described above in relation to  FIGS. 5 and 6 . The compliant member  44  of the embodiment shown in  FIG. 8  can be fixedly attached to the housing  64  and slidably contact the movable element  70 , or may alternatively not be fixed to either the housing or the movable element  70 .  
       FIGS. 9-13  show exemplary embodiments of damping elements  24 , according to the invention, in which the movable element  70  is rotatable about the axis  68 .  
       FIGS. 9 and 10  show two views of a damping element  24  wherein the movable element  70  includes one or more paddles  74  extending therefrom. The paddles  74  may one or more hole  76  therein, as shown in  FIGS. 14   a - 14   c , for passage of the MR fluid  32  therethrough, and wherein application of magnetic flux to the MR fluid  32  in the cavity  27  from the coil  70  increases resistance to the passage of MR fluid  32  through the holes  76  in the paddles  74 .  
      In the embodiment of the damping element  24  shown in  FIGS. 9 and 10 , the electrical coil extends around an outer periphery of the housing  64 .  FIG. 11  shows an embodiment of a damping element  24 , according to the invention, in which the electrical coil  71  is located inside of the cavity defined by the bore  66  of the housing  64 , and the movable element is contoured to wrap partially around the coil  71 .  
      The embodiment of  FIG. 9 , also includes a permanent magnet  36 , disposed adjacent the MR fluid  32 . The permanent magnet  36  may be moved along the axis  68  to set a threshold value of viscosity of the MR fluid  32 . In embodiments of the invention that do not have an electromagnet, a threshold value may also be set, using an electromagnet  58 , by applying a continuous base signal level that is modulated to actively control the damping provided by the MR fluid  32 .  
       FIGS. 12 and 13  show an embodiment of a damping element  24  having a rotatable movable element  70  and a compliant member  44  disposed within the bore  66  and operatively connected between the movable element  70  and the housing  64 , with the compliant member  44  including a porous segment  46  having one of the one or more cavities  27  (as shown in  FIGS. 5 and 6 ) therein containing the MR fluid  32 . Application of a magnetic field from the coil  58  to the MR fluid  32  changes the stiffness of the compliant member  44 , to thereby change the damping provided.  
      The porous segment  46  of the compliant member  44  may be sponge-like, or fibrous, as described above in relation to  FIGS. 5 and 6 . The compliant member  44  of the embodiments shown in  FIGS. 12 and 13  can be fixedly attached to the housing  64  and slidably contact the movable element  70 , or conversely be fixedly attached to the movable element  70  and slidably contact the housing  64 , or may alternatively not be fixed to either the housing  64  or the movable element  70 , in various embodiments of the invention. For example, in embodiment shown in  FIG. 12 , the compliant member  44  is sponge-like, fixedly attached to the movable element  70 , and slidingly contacts a side wall  76  of the housing  64 . In embodiment shown in  FIG. 13 , the compliant member  44  is a fibrous material, fixedly attached to the movable element  70 , and slidingly contacts an end wall  78  of the housing  64 .  FIGS. 15   a -I Se show yet other configurations for attaching a compliant member  44  having a porous segment  46  to a rotatable movable element  70 , according to the invention.  
      In the embodiment of  15   d  the porous segments  46  is fibrous, and has a fiber direction (shown by arrows  80 ) extending primarily perpendicular to the axis  68 . In the embodiment of  15   e  the porous segments  46  is fibrous, and has a fiber direction  80  extending primarily parallel to the axis  68 . By orienting the fibers in a particular direction, the change in stiffness can be made directionally sensitive.  
      In embodiments of the invention having a movable element  70  operatively connected through a compliant member  44  to interact with a housing  64 , such as those embodiments shown in  FIGS. 8, 12 ,  13 , and  15   a - 15   e , it is preferable that the MR fluid be confined within the compliant member  44 , rather than filling the inside of the housing  64  around the movable element  70 , but this is not a requirement of the invention. MR fluid tends to be relatively expensive, and it is thus desirable to minimize the amount of MR fluid that is required, by containing it within the compliant member  44 . It is contemplated, however, that in some embodiments of the invention, it may be desirable to have the movable element  70  and/or the compliant member  44  disposed in a cavity of the housing  64  that is at least partially filled with MR fluid.  
      Those skilled in the art will readily recognize that, while the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention.  
      For example,  FIGS. 16   a - 16   c  show alternate embodiments of an input device  18 , having an input element in the form of a push button  22 , for receiving a linear input  26 , in which the button  22  is supported on a surface  20  by a conical skirt  54  of resilient material, forming a spring, and several buttons  56  of compliant material, with a common electrical coil  58  extending around all of the buttons  56  of compliant material.  
       FIGS. 17   a  and  17   b  show an alternate embodiment of an input device  18 , having an input element in the form of a push button  22 , for receiving a linear input  26 , in which the button  22  is supported on a surface  20  by a conical skirt  54  of resilient material, forming a spring. The push button  22  includes downwardly extending legs  82  that form the movable elements of one or more damping elements  24 , each having a cavity  27  containing MR fluid  32 , and a coil  58  disposed around the cavity  27 . Alternatively, the damping element  24  may include a compliant member  44  forming one or more cavities  27  containing MR fluid  32 , with the coil  58  either surrounding or being embedded in the compliant member  44 .  
       FIGS. 18   a  and  18   b  show other alternate embodiments of an input device  18 , having an input element in the form of a push button  22 , for receiving a linear input  26 , in which the button  22  is supported on a surface  20  by a conical skirt  54  of resilient material, forming a spring, and a sheet or disk  84  of compliant material, with one or more electrical coils  58  disposed under the sheet or disk  84  of compliant material. In the embodiment shown in  FIG. 18   a , the coil  58  rests on the surface  20 , and in the embodiment of  FIG. 18   b , the coil  58  is supported by the conical skirt  54  of resilient material.  
      It is contemplated that the invention may be used to significant advantage in many types of control applications for limiting motions/movements of a joystick and/or any device that uses linear and/or rotary motions.  
      For example, the invention may be utilized in a control system that limits one motion/movement to recognize and obey 2D linear controlled boundaries. An example of such an application is a controlled landing of an aircraft. The aircraft&#39;s steer-by-wire software limits motions/movements of the MR controlled joystick/device to prevent the plane form landing beyond left and/or right edges of a landing strip. Control software, using parameters for the landing strip that are stored in a database or uploaded from a transmitter at the landing strip, prevents the operator (pilot in this example) from moving an input element in such a way as to direct the aircraft beyond recognized limits of landing strip. A rotary element attached to a steering wheel, for example, will prevent movement of the joystick/device to a position that would steer the aircraft beyond the left or right edges of the landing strip, to thereby prevent pilot error.  
      The invention may also be used in a control system that limits two motions to recognize and obey 2D non-linear boundaries. An example of such an application is a controlled laser surgery device where safe boundaries of laser cuts are recognized by software and are ensured by MR controlled devices. Control software prevents the operator (surgeon in this example) from cutting beyond safe and recognized 2D limits of surgical cut areas, thereby preventing human error and helping the surgeon to minimize cuts.  
      In other embodiments of a control system, the invention is used to limit three motions by recognizing and obeying 3D linear and/or non-linear boundaries. An example of application is a controlled laser surgery joystick/device where safe boundaries of laser shape and depth of the cut are assured. Control software prevents the operator (surgeon in this example) from cutting beyond safe and recognized 3D limits of surgical cut areas, to thereby prevent human error and help the surgeon to minimize cuts.  
      It will be further recognized, by those skilled in the art, that MR controlled devices, according to the invention, can be controlled to follow any software-controlled trajectory by limiting motions/movements of a joystick and/or any device that uses linear and/or rotary motions.  
      For example, a software-controlled trajectory may limit one motion/movement, to recognize and follow a 2D linear controlled trajectory. An example of application is a controlled landing of an aircraft. The aircraft&#39;s steer-by-wire software restricts motions/movements of the MR controlled joystick/device to follow a software-controlled landing trajectory by limitation of one 2D motion/movement to recognize and follow a desired linear controlled trajectory. Control software helps the operator (pilot in this example) to operate with optimum performance by controlling the MR damper in such a manner that the pilot is prevented from making movements of the joystick that would cause the aircraft to deviate from the desired trajectory.  
      A software-controlled trajectory may also limit two motions/movements, to recognize and follow a 2D linear controlled trajectory. An example of such an application is a controlled laser surgery device where optimum laser cuts are assured. MR controlled devices, according to the invention, restrict motions/movements of a joystick to follow a software-controlled laser-cutting trajectory by limiting two motions/movements to recognize and follow a linear controlled trajectory. Control software helps the operator (surgeon in this example) to operate with optimum performance, by preventing human error and helping the surgeon to minimize cuts.  
      In other embodiments of a control system using the invention, a software-controlled trajectory may limit three motions/movements, to recognize and follow a 3D linear, and/or a non-linear controlled trajectory. An example of such an application is a controlled laser surgery device where an optimized 3D laser cut can be assured. Control software controls an MR damper, according to the invention, to keep the operator (surgeon in this example) within safe and recognized 3D limits of surgical cut areas, to thereby prevent human error and help the surgeon to minimize cuts.  
      The scope of the invention is indicated in the appended claims, and all changes or modifications within the meaning and range of equivalents are intended to be embraced therein.