A robot system has first and second joint control units that respectively calculate first and second current values to be supplied to first and second motors based on deviations between first and second operation targets for the motors that are input from a higher device and actual operation of output shafts of the motor, and control operation of the output shafts by supplying current to the motors based on the current values, and an error estimation unit estimating an error in operation of a second joint due to bending and/or twisting of a robot arm based on the first current value and the actual operation of the output shaft of the first motor, in which the second joint control unit calculates the second current value to control the rotation angle of the output shaft of the second motor in a manner compensating for an angle error of the second joint.

a speed reducer angular transmission error identification system including a variation data acquisition unit that acquires first variation data indicating a periodic variation of an operation of a second joint caused by a first motor's angular transmission error when a first joint control unit rotates a first motor's output shaft in a first direction at a constant first target speed and a second joint drive unit rotates an output shaft of a second motor at a constant second target speed, second variation which is data indicating a periodic variation of an operation of second joint caused by the first motor's angular transmission error when the first joint control unit rotates the first motor's output shaft in a second direction at the constant first target speed and the second joint control unit rotates the second motor's output shaft at the constant second target speed.

An angular transmission error identification system that identifies an angular transmission error of a speed reducer of a robot arm including a joint that is rotationally driven by a motor via the speed reducer, including an identification unit that calculates amplitude and phase parameters of an angular transmission error identification function, which is a periodic function that models an angular transmission error of the speed reducer and has the parameters, and identifies the error using the function, wherein the unit calculates an amplitude parameter corresponding to a gravitational torque current value which is a value acting on a joint when the error is identified using a first or second amplitude function according to a value of the gravitational torque current value, and calculates a phase parameter corresponding to the gravitational torque current value using a first or second phase function according to a value of the gravitational torque current value.

An angular transmission error identification system that identifies an angular transmission error of a speed reducer of a robot arm including a joint that is rotationally driven by a motor via the speed reducer, including an identification unit that calculates amplitude and phase parameters of an angular transmission error identification function, which is a periodic function that models an angular transmission error of the speed reducer and has the parameters, and identifies the error using the function, wherein the unit calculates an amplitude parameter corresponding to a gravitational torque current value which is a value acting on a joint when the error is identified using a first or second amplitude function according to a value of the gravitational torque current value, and calculates a phase parameter corresponding to the gravitational torque current value using a first or second phase function according to a value of the gravitational torque current value.

a speed reducer angular transmission error identification system including a variation data acquisition unit that acquires first variation data indicating a periodic variation of an operation of a second joint caused by a first motor's angular transmission error when a first joint control unit rotates a first motor's output shaft in a first direction at a constant first target speed and a second joint drive unit rotates an output shaft of a second motor at a constant second target speed, second variation which is data indicating a periodic variation of an operation of second joint caused by the first motor's angular transmission error when the first joint control unit rotates the first motor's output shaft in a second direction at the constant first target speed and the second joint control unit rotates the second motor's output shaft at the constant second target speed.

A robot system has first and second joint control units that respectively calculate first and second current values to be supplied to first and second motors based on deviations between first and second operation targets for the motors that are input from a higher device and actual operation of output shafts of the motor, and control operation of the output shafts by supplying current to the motors based on the current values, and an error estimation unit estimating an error in operation of a second joint due to bending and/or twisting of a robot arm based on the first current value and the actual operation of the output shaft of the first motor, in which the second joint control unit calculates the second current value to control the rotation angle of the output shaft of the second motor in a manner compensating for an angle error of the second joint.

A drive unit for a robot, having an input shaft, an input shaft drive motor and a strain wave gear mechanism for transmission to an output shaft. The strain wave gear mechanism has a wave generator which is operatively connected to the input shaft, a flexible ring and a toothed ring are connectable to the output shaft, a first sensor for detecting an angular position of the input shaft and a second sensor for detecting the angular position of the output shaft. In order to allow the drive unit to precisely adjust the angular position of the output shaft to each setpoint angular position, the drive unit has a third sensor for detecting an expansion of the flexible ring. A robot having such a drive unit and a method for precisely adjusting the angular position of the output shaft are also provided.

A positioning control device of an actuator provided with a strain wave gearing has a full-closed control system for feeding back a position of a load shaft, and driving and controlling a motor so as to position the load shaft at a target position. The full-closed control system has an H compensator designed so that, when a generalized plant having angular transmission error in the strain wave gearing as a disturbance input is assumed, an H norm of a transfer function from the disturbance input of the generalized plant to an evaluation output is a predetermined value or less. Mechanical vibration during positioning response caused by angular transmission error in the strain wave gearing can be reliably suppressed.

A positioning control device of an actuator provided with a strain wave gearing has a full-closed control system for feeding back a position of a load shaft, and driving and controlling a motor so as to position the load shaft at a target position. The full-closed control system has an H compensator designed so that, when a generalized plant having angular transmission error in the strain wave gearing as a disturbance input is assumed, an H norm of a transfer function from the disturbance input of the generalized plant to an evaluation output is a predetermined value or less. Mechanical vibration during positioning response caused by angular transmission error in the strain wave gearing can be reliably suppressed.

A method for reducing kinematic error in a joint includes providing an acceleration sensor; selecting a trajectory to be followed by the acceleration sensor; estimating expected acceleration values the sensor will experience along the trajectory; outputting initial commands for moving the sensor along the trajectory; obtaining corrected commands by adding to a parameter specified in an initial command a kinematic error correction and inputting the corrected commands into a joint controller; recording acceleration values to which the sensor is subject while moving according to the corrected commands; judging whether a deviation between the expected acceleration values and the recorded acceleration values exceeds a predetermined threshold, and when the deviation is judged to exceed the threshold, modifying the kinematic error correction so as to reduce the deviation.