Harmonic Drive Systems Inc.

Nagoya Institute of Technology

Kozo Sasaki

Makoto Iwasaki

Yoshifumi Okitsu

Toshiki Maruyama

Yuki Kato

Toshio Yajima

Naoki Kanayama

Muneo Mitamura

Toshiyuki Abe

Yuichi Mizuguchi

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

A motor rotational position detecting method detects the magnetic pole position of each phase of a three-phase AC servomotor, generates a three-phase square wave signal having a phase difference of 120 degrees, allocates data on the rotational position of a motor shaft to the edge of each square wave signal, calculates the rotational speed of the motor on the basis of the elapsed time from the previous edge detection point to this time edge detection point, and estimates the rotational position of the motor shaft at a certain period and outputs it on the basis of the rotational speed of the motor and the rotational position allocated to this time edge in the rotational section from this time edge detection point to the next edge detection point. As a result, a detection mechanism can be constructed with a small installation space and at low cost and the output of a high-resolution encoder can be obtained in a pseudo manner.

Rotational position detecting method for AC servomotor and simple encoder

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.

Method for compensating for angular transmission error of an actuator

The power-off electromagnetic brake () attracts an armature that is pressed by a spring force to a rotating member by a magnetic attraction force that is generated by energizing an exciting coil, and brake force that is acting on the rotating member is released. A voltage control circuit () continuously energizes the exciting coil for a fixed length of time and generates a considerable magnetic attraction force in order to attract the armature to a yoke when a brake power source () is switched on during brake release. After the armature has been attracted to the yoke, the voltage control circuit () intermittently energizes the exciting coil at a set cycle and a set on/off duty ratio to hold the armature in an attracted state to the yoke, thereby reducing power consumption and heat generation.

Power-off electromagnetic brake

A multiple-rotation absolute encoder attached to an actuator provided with a motor and a reduction gear comprises a multiple-rotation value counter for counting a multiple-rotation value representing a number of rotations of a rotating shaft of the motor from a predetermined origin; a memory part for storing a reduction ratio R of the reduction gear; and a counter-controlling part for setting a range of the count value of the multiple-rotation value counter from zero rotations to (R&#x2212;1) rotations on the basis of the reduction ratio R stored and maintained in the memory part, resetting the count value to zero when the rotating shaft makes a single rotation in a forward direction from a state in which the count value is (R&#x2212;1), and setting the count value to (R&#x2212;1) when the rotating shaft makes a single rotation in a reverse direction from a state in which the count value is zero. The rotation-angle position within a single rotation of the output shaft can be specified without the multiple-rotation value counter overflowing, even when the actuator rotates continuously in one direction.

Multiple-rotation absolute encoder

In the magnetic absolute encoder, an ordinary operating circuit and an ordinary/backup operating circuit are actuated during ordinary operation in which power is supplied from the ordinary operating power supply; the single-rotation absolute value (1) and single-rotation absolute value (2) detected by these circuits are compared by the abnormality diagnosis circuit, and the presence or absence of an abnormality is automatically judged During backup in which the ordinary operating power supply is interrupted, only the low-power-consumption ordinary/backup operating circuit is actuated, and the multiple-rotation value (2) is detected At the point in time at which the system is returned to ordinary operation, the multiple-rotation value setting circuit sets the multiple-rotation value (2) as the multiple-rotation value (1) of the ordinary operating circuit. As a result, the calculation operation of the multiple-rotation value (1) can be restarted.

Magnetic absolute encoder

A servo driver () includes: an input section () for input-specifying the type of an encoder () at the side of an actuator (); a control section () for generating a control signal () according to the type input; and an encoder signal processing IC () for switching the input port to which reception data (S) is input form the encoder () according to the control signal (). The encoder signal processing IC () is compatible with processing of an output of either a line-saving encoder or a 14-line encoder and can realize a highly general-purpose servo driver. This can solve the problem that the servo driver should be modified according to the type of the encoder mounted on the actuator.

Servo driver and encoder signal processing IC

A method of correcting positional error in an actuator that is equipped with a motor and a wave gear reduction drive that transmits a motor output to the target load. Positioning error relative to the absolute position of the actuator output shaft is measured, to compile error correction data relating to each position on the rotation of the motor shaft. The rotational position of the motor shaft is detected and rotational position correction information produced by adding error correction values assigned to the position concerned. The rotational positional error information thus produced is used as position feedback information for controlling the positioning of the output shaft.

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Azumino, Japan

Kozo Sasaki