Harmonic Drive Systems Inc.

Nagoya Institute of Technology

Yoshifumi Okitsu

Makoto Iwasaki

Kozo Sasaki

Masafumi Yamamoto

Yuki Kato

Toshio Yajima

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&#x221e; 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&#x221e; 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.

Positioning control device of actuator provided with strain wave gearing using H-&#x221e; control

A positioning control system is provided with a state-feedback control system with a state observer as a full-closed control system for driving and controlling a motor so that a load shaft, which is an output shaft of a strain wave gearing, is positioned at a target position on the basis of a load shaft position actually detected. The state observer estimates a motor shaft position and a motor velocity based on a control input for the motor and the load shaft position. The state-feedback control system feeds back the state quantity of the object of control using the load shaft position as well as estimated motor shaft position and estimated motor velocity obtained by the state observer. It is possible to suppress resonant vibration caused by angular transmission error in the strain wave gearing and perform highly accurate positioning.

Positioning control device for actuator provided with strain wave gearing using full-closed control with state observer

A positioning control system for an actuator provided with a strain wave gearing is provided with: a semi-closed feedback controller FB(s) that controls a load shaft position &#x3b8;on the basis of a feedback motor shaft position &#x3b8;; and a feedforward linearization compensator configured by incorporating a nonlinear plant model for an object to be controlled into a feedback linearization compensator using an exact linearization technique. The feedforward linearization compensator uses a forward-calculated state quantity estimated value x* to calculate a feedforward current instruction i*and a feedforward motor position instruction &#x3b8;*to be input into the feedback controller FB(s). A positioning error caused by a non-linear element (non-linear spring property, relative rotational synchronization component, and non-linear friction) of the strain wave gearing is compensated for by the feedforward linearization compensator.

Positioning control system for actuator provided with wave gear device

In a positioning apparatus for an actuator, a sliding mode controller for compensating for nonlinear characteristics of a wave gear device of the actuator generates a control input u to a controlled object, based on a position command &#x3b8;* and a state variable x for expressing the controlled object. The controlled object is defined in the following formula.* The switching surfaces of the sliding mode control system are defined by a variable S expressed in the following formula. The control input u is the sum of the linear-state feedback control term uand the nonlinear control input u where &#x3c3; is the switching function, and k is the switching gain.

Positioning apparatus for actuator with wave gear device

According to a method for performing adaptive friction compensation of an actuator including a wave gear drive, there is used as a friction compensation current applied to a motor drive current a static friction compensation current iwhen a motor shaft stops with a deviation, and a Coulomb friction compensation current iin other circumstances. The static friction compensation current iis obtained by adding a compensation amount iof a monotonically increasing ramp function to a compensation amount iof a step function, and a step-function compensation amount iis used as the Coulomb friction compensation current i. Since the amount of friction compensation can be changed adaptively based on the data during positioning-control response, a motor shaft can be stabilized at a target angle without prominent accompanying vibration, even if the ambient temperature changes and the friction characteristics of the wave gear drive fluctuate.

Method for performing adaptive friction compensation in an actuator accounting for variation in friction characteristics of wave gear drive accompanying change in temperature

A method for controlling positioning of an actuator having a wave gear device uses an exact linearization technique to compensate effects relative to positioning control of a load shaft caused by the non-linear spring characteristics of the wave gear device. A plant model is constructed from the actuator, and linearized using the exact linearization technique; measurements are taken of non-linear elastic deformation of the wave gear device relative to load torque; the non-linear spring model &#x3c4;g(&#x3b8;tw) is defined using a cubic polynomial with the constant defined as zero to allow the measurement results to be recreated; and the current input into the model and motor position of the model when a load acceleration command is a command value are entered into a processor arranged as a semi-closed loop control system for controlling positioning of the load shaft, as a feed-forward current command and a feed-forward motor position command.

Method for controlling positioning of actuator comprising wave gear device

A positioning system () provided with an actuator () having a wave gear device () is driven and controlled by a semi-closed loop control for controlling the load position of a load device () based on the motor position of a motor shaft () of a motor (). In a method for compensating for an angular transmission error by compensating for a motor shaft synchronous component &#x3b8;Sync that occurs in synchrony with the motor position and is a relative rotation-synchronous component that includes an angular transmission error component of the wave gear device (), the positioning system () is represented as a two-inertia model, and the motor shaft synchronous component &#x3b8;Sync is represented as an oscillation source for producing a twisting action between the two inertia bodies in the two-inertia model. A motor current command iref is corrected by a compensation current command icomp calculated so as to allow the effect of the motor shaft synchronous component &#x3b8;Sync on the load position to be compensated in this case, and a motor position command r is corrected by a motor position correction signal &#x3b8;comp calculated in order to compensate for the effect of the motor shaft synchronous component &#x3b8;Sync.

Method for compensating for angular transmission error of wave gear device

The non-linear elastic deformation component included in the angular transmission error of an actuator provided with a wave gear drive is a component of the angular transmission error occurring due to elastic deformation of a flexible externally-toothed gear when the direction of rotation of the motor shaft changes. This component can be analyzed by driving the motor in a sine-wave shape. A model of the non-linear elastic deformation component (non-linear model) obtained from the analysis results is used to store data or a function for compensating for this component in a motor-control device. Compensation for the non-linear elastic deformation component (&#x3b8;) is added to a motor-shaft angle command (&#x3b8;*) as a compensation input (N&#x3b8;*) for feed-forward compensation. As a result, the non-linear elastic deformation component (&#x3b8;) can be effectively reduced, and the positioning precision of the actuator can be improved.

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Azumino, Japan

Yoshifumi Okitsu