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AssigneeMassachusetts Institute of Technology
InventorsGuillaume Morel, Steven Dubowsky
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An elegant, cost-effective apparatus and method is disclosed for compensating the effect of joint friction in manipuulators. The invention uses a six axis wrench sensor (also called a force/torque sensor) mounted between the manipulator and a reference body upon which it is supported. From the base wrench measurements, for rotary joints, the joint torques are estimated. The estimation apparatus uses Newton-Euler relations of successive link bodies. The estimated torque is fed back through a torque controller, that virtually eliminates friction and gravity effects. A position control loop encloses the torque controller and provides it with desired torques computed from measured position errors. For linear joints, appropriate forces are estimated. Coupled to link position sensors and the wrench sensor, is a gravity compensator, which generates a dynamic wrench signal that corresponds to the gravity compensated dynamic component of the base wrench signal, based on the position signals and the base wrench signal. Coupled to the gravity compensator and the position sensors is a joint analyzer, which generates a signal that corresponds to the gravity compensated torque that is actually applied to the link at the rotary joint, based on the dynamic wrench signal and the position signals. Both torques at rotary joints and forces at linear joints are estimated by the apparatus. Multiple and single joint manipulators can be evaluated. The achieved precision is substantially greater than for conventional methods and approaches the resolution of the Puma's encoders.
An apparatus for generating a signal that corresponds to the gravity compensated torque actually applied to a link at a rotary joint of a manipulator, said manipulator having a base that is connected to a reference body and a plurality of moveable links, the first being connected to said base through a first joint and each other moveable link being connected through a joint to an adjacent link that is kinematically closer to said reference body, and for each of said movable links, a position sensor that generates a position signal that corresponds to the position of said link relative to said respective adjacent link, said signal generating apparatus comprising:
An apparatus for generating a signal that corresponds to the gravity compensated force actually applied to a link at a linear joint of a manipulator, said manipulator having a base that is connected to a reference body and a plurality of moveable links, the first being connected to said base through a first joint and each other moveable link being connected through a joint to an adjacent link that is kinematically closer to said reference body, and for each of said movable links, a position sensor that generates a position signal that corresponds to the position of said link relative to said respective adjacent link, said signal generating apparatus comprising:
An apparatus for generating a signal that corresponds to the gravity compensated torque actually applied to a link at a rotary joint of a manipulator, said manipulator having a base that is connected to a reference body, and a moveable link that is connected to said base through said rotary joint, and a position sensor that generates a position signal that corresponds to the position of said link relative to said base, said signal generating apparatus comprising:
An apparatus for generating a signal that corresponds to the gravity compensated force actually applied to a link at a linear joint of a manipulator, said manipulator having a base that is connected to a reference body, and a moveable link that is connected to said base through said linear joint, and a position sensor that generates a position signal that corresponds to the position of said link relative to said base, said signal generating apparatus comprising:
A method for generating a signal that corresponds to the gravity compensated torque actually applied to a link at a rotary joint of a manipulator, said manipulator having a base that is connected to a reference body and a plurality of moveable links, the first being connected to said base through a first joint and each other moveable link being connected through a joint to an adjacent link that is kinematically closer to said reference body, and for each of said movable links, a position sensor that generates a position signal that corresponds to the position of said link relative to said adjacent link, said signal generating method comprising the steps of:
A method for generating a signal that corresponds to the gravity compensated force actually applied to a link at a linear joint of a manipulator, said manipulator having a base that is connected to a reference body and a plurality of moveable links, the first being connected to said base through a first joint and each other moveable link being connected through a joint to an adjacent link that is kinematically closer to said reference body, and for each of said movable links, a position sensor that generates a position signal that corresponds to the position of said link relative to said adjacent link, said signal generating method comprising the steps of:
A method for generating a signal that corresponds to the gravity compensated torque actually applied to a link at a rotary joint of a manipulator, said manipulator having a base that is connected to a reference body and that is connected to said moveable link through said rotary joint and a position sensor that generates a position signal that corresponds to the position of said link relative to said base, said signal generating method comprising the steps of:
A method for generating a signal that corresponds to the gravity compensated force actually applied to a link at a linear joint of a manipulator, said manipulator having a base that is connected to a reference body and that is connected to said moveable link through said linear joint and a position sensor that generates a position signal that corresponds to the position of said link relative to said base, said signal generating method comprising the steps of:
Dependencies are inferred from the claim text.