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US 4,980,625 AGranted
Apparatus and method for servo control system
AssigneeSeiko Instruments Inc.
InventorAkira Shimada
Life of this patent
Estimating the term…
Abstract
The present invention is provided to suppress mechanical resonance which is likely to be generated in a mechanically driven and controlled apparatus such as robots, machine tools, etc. due to their low rigidity. In order to achieve this object, the present invention uses an adaptive filter which changes its cut-off frequency or notch frequency in response to a change in the natural oscillation frequency caused by a change in position and orientation of and load acting on the machine.
Claims16
In combination:
- a machine having a mechanical resonance frequency, and a control apparatus for controlling the machine;
- the machine comprising,
- an actuator for generating mechanical power in response to output command data;
- an effector for performing a commanded work;
- and
- a transmitter for transmitting mechanical power from said actuator to said effector;
- wherein at least one of said actuator, said effector and said transmitter has a finite mechanical rigidity;
- and
- the control apparatus comprising,
- detecting means for detecting a change of mechanical condition which affects the inertia moment of the machine;
- servo compensating calculator means operative in response to input command data and output data of said detecting means for calculating and outputting a compensating result data effective to make the machine move in accordance with said input command data;
- and
- adaptive filter means for filtering said compensating result data to suppress frequency components close to the mechanical resonance frequency of the machine, the mechanical resonance frequency changing in dependence on the change of said inertia moment of the machine, in response to said output data of said detecting means, and outputting output command data to the machine.
10 more elements
A method of servo control for a machine having a mechanical resonance frequency, comprising the steps of :
- detecting a change of mechanical condition which affects the inertia moment of the machine at given sampling times;
- calculating a servo compensating result data effective to make the machine move in accordance with position data and command data in response to said detected mechanical condition and said position data and command data;
- filtering said servo compensating result data to suppress frequency components close to said mechanical resonance frequency of the machine in response to said detected mechanical condition, the filtering step comprising
- calculating an inertia moment of the machine in response to said detected mechanical condition,
- calculating the mechanical resonance frequency using the inertia moment and an elasticity constant of a transmission mechanism,
- calculating filter coefficients using the mechanical resonance frequency, and
- calculating torque command data using a plurality of servo compensating result data and a plurality of torque command data taken at previous sampling times and the filter coefficients;
- and
- outputting the filtered result data to the machine as torque command data before the next sampling time.
6 more elements
Apparatus for suppressing mechanical resonance of a driven machine, comprising:
- drive means for driving a machine in accordance with command data applied thereto whereby the machine undergoes unwanted vibrations as a result of being driven;
- detecting means for detecting a change in at least one of the position, orientation and loading conditions of the driven machine and providing present condition data representative of the detected present condition of the machine;
- servo means responsive to the present condition data and to input command data representative of the desired movement of the machine for producing therefrom compensated command data effective to control the movement of the machine so that the machine moves in accordance with the input command data, the compensated command data having a frequency of vibration characteristic which includes the resonant frequency of the machine;
- and adaptive filter means for filtering the compensated command data to suppress frequency components near to and including the resonant frequency and applying the filtered compensated command data to the drive means to thereby suppress mechanical resonance of the driven machine.
1 more element
Dependencies are inferred from the claim text.