Gyro-stabilized platforms for force-feedback applications

Abstract

Force feedback in large, immersive environments is provided by device which a gyro- stabilization to generate a fixed point of leverage for the requisite forces and/or torques. In one embodiment, one or more orthogonally oriented rotating gyroscopes are used to provide a stable platform to which a force-reflecting device can be mounted, thereby coupling reaction forces to a user without the need for connection to a fixed frame. In one physical realization, a rigid handle or joystick is directly connected to the three-axis stabilized platform and using an inventive control scheme to modulate motor torques so that only the desired forces are felt. In an alternative embodiment, a reaction sphere is used to produce the requisite inertial stabilization. Since the sphere is capable of providing controlled torques about three arbitrary, linearly independent axes, it can be used in place of three reaction wheels to provide three-axis stabilization for a variety of space-based and terrestrial applications.

What is claimed is: 
     
       1. A spatially unrestricted force-feedback device, comprising:
 a body;   gyroscopic means connected to the body to provide an inertial reference to stabilize the body in at least one spatial dimension;   a user-interactable member connected to the body; and   force-feedback means coupled to the member, enabling a user of the device to experience the feedback of forces relative to the gyroscopically stabilized body.   
     
     
       2. The device of  claim 1 , wherein the user-interactable member is a joystick. 
     
     
       3. The device of  claim 1 , wherein the user-interactable member includes a handle. 
     
     
       4. The device of  claim 1 , wherein the user-interactable member is a steering wheel. 
     
     
       5. The device of  claim 1 , wherein the user-interactable member is a device associated with the simulation of a sport. 
     
     
       6. The device of  claim 1 , further including:
 a computer system modeling a virtual environment including one or more virtual objects; and wherein   the user-interactable member is in electrical communication with the computer system to generate forces on the member as a function of an activity involving an object within the virtual environment.   
     
     
       7. The device of  claim 1 , wherein the gyroscopic means includes a momentum wheel, and wherein a torque is produced on the member through accelerating and decelerating the angular velocity of the wheel. 
     
     
       8. The device of  claim 7 , including three momentum wheels to stabilize the body in three dimensions. 
     
     
       9. The device of  claim 1 , wherein the gyroscopic means takes the form of a reaction sphere operative to produce arbitrary reaction torques about three linearly independent axes of the body. 
     
     
       10. The device of  claim 1 , further including an angular position measuring device to determine the state of the body in space. 
     
     
       11. The device of  claim 10 , wherein the angular position measuring device is a potentiometer. 
     
     
       12. The device of  claim 10 , wherein the angular position measuring device as an encoder. 
     
     
       13. The device of  claim 1 , further including an angular velocity measuring device to determine the state of the gyroscopic means. 
     
     
       14. The device of  claim 13 , wherein the angular velocity measuring device is a tachometer. 
     
     
       15. The device of  claim 13 , wherein the state of the gyroscopic means is determined by numerically differentiating the angular position of the body. 
     
     
       16. The device of  claim 1 , further including an active control system to provide device stability. 
     
     
       17. A spatially unrestricted force-feedback device, comprising:
 a body;   an active control system to stabilize the body in space;   three rotatable reaction wheels coupled to the body;   means for determining the angular velocity of each wheel;   an angular position measuring device to determine the state of the body in the space;   a user-interactable member connected to the body; and   force-feedback means using the angular velocity and position of the body as inputs to produce torque on the member about three arbitrary axes through the coordinated acceleration and deceleration of the angular velocity of each wheel.   
     
     
       18. The device of  claim 17 , wherein the angular position measuring device is an inertial measuring unit. 
     
     
       19. The device of  claim 17 , wherein the angular velocity measuring device uses numerical differentiation to determine the angular position of the body. 
     
     
       20. A method of generating a spatially unrestricted haptic environment, comprising the steps of:
 providing a body in space having a user-interactable force-feedback device;   geo-stabilizing the body in one or more dimensions;   simulating a virtual environment modeling one or more virtual objects; and   interfacing the user-interactable force-feedback device to the virtual environment, enabling the user to experience a force representative of an activity within the virtual environment involving one or more of the objects.   
     
     
       21. The method of  claim 20 , further including the step of:
 slowly and continually removing angular momentum from the body so as to minimize the effect on a user.   
     
     
       22. The method of  claim 20 , further including the steps of:
 receiving an input disturbance on the body;   stabilizing the body through a pole placement, with the location of the poles being determined through optimal control theory; and   canceling out the disturbance inputs to produce a desired torque output immune to the input disturbance.   
     
     
       23. The method of  claim 20 , further including the step of:
 receiving an external force generated through a remote physical device; and   producing a scaled representation of the force received relative to a point on the physical device.   
     
     
       24. The method of  claim 23 , wherein the scaled representation is such that the maximum force applicable to the physical device is mapped into the maximum force which the device is capable of producing. 
     
     
       25. A spatially unrestricted force-feedback device, comprising:
 a first body;   a plurality of motors, each of said motors capable of imparting an inertial force about an associated axis of rotation to change rotational momentum of a spinning body, each of said motors connected to said first body to provide computer controllable tactile sensations on said first body about said associated axis, the tactile sensations provided by changing the rotational momentum of the spinning body to cause a torque to be applied to the first body;   a user-interactable member connected to said first body, wherein said user-interactable member is in communication with a host computer system modeling a simulated environment including one or more simulated objects, said host computer system commanding said tactile sensations on said first body as a function of a simulated activity involving at least one object within said simulated environment; and   a computer mediated controller electrically connected to said motors and in communication with said host computer system, said controller receiving signals from said host computer system and simultaneously controlling each of said motors in response such that said motors produce said inertial forces about said axes, and said controller sending data to said host computer system, said data responsive to user manipulation of said user-interactable member.   
     
     
       26. A spatially unrestricted force-feedback device as described in claim 25, wherein said computer mediated controller decodes commands received from said host computer system. 
     
     
       27. A spatially unrestricted force-feedback device as described in claim 25, wherein said computer mediated controller decodes commands received on a serial communication bus. 
     
     
       28. A spatially unrestricted force-feedback device as described in claim 25, wherein said user-interactable member is a joystick. 
     
     
       29. A spatially unrestricted force-feedback device as described in claim 25, wherein said user-interactable member is a steering wheel. 
     
     
       30. A spatially unrestricted force-feedback device as described in claim 25, wherein said user-interactable member is associated with the simulation of a sport. 
     
     
       31. A spatially unrestricted force-feedback device as described in claim 25, wherein said computer mediated controller includes a processor that runs motor control code stored in Read-Only memory. 
     
     
       32. A spatially unrestricted force-feedback device as described in claim 25, wherein at least a portion of said computer controllable inertial forces stabilize said first body in at least one spatial dimension to counteract undesired torques produced by at least one of said motors. 
     
     
       33. A spatially unrestricted force-feedback device as described in claim 25, wherein said computer controllable inertial forces stabilize said first body in at least one spatial dimension.