Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1999-11-24
2001-09-25
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S249000, C700S250000, C700S253000, C700S256000, C700S258000, C700S260000, C700S261000, C700S262000, C318S568110, C318S568140, C318S568150, C318S568160, C318S568170, C318S568180, C318S568190, C701S023000, C901S050000, C901S023000, C901S035000
Reexamination Certificate
active
06295484
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a robot control device for controlling a multiaxial robot such as an industrial robot, and more particularly to a method of and a device for controlling a robot to suppress vibrations produced by mechanical interference between axes.
BACKGROUND ART
Generally, industrial robots whose axes are controlled by electric motors actuate arms under loads via gears of a harmonic drive or the like having a large speed reduction ratio in order to compensate for a power shortage of the electric motors and minimize the effect of disturbing forces from the loads. Because of the intermediary gears with the large speed reduction ratio, mechanical interference between control axes has heretofore not posed significant problems. However, recent growing demands for high-speed and high-precision robot operation focus on problems caused by a mechanical effect that cannot be compensate for by a PI (proportional plus integral) control process and disturbance that cannot be ignored even though the arm is actuated with the high speed reduction ratio.
The present applicant has already proposed an invention disclosed in Japanese laid-open patent application No. Hei 9-222910 (JP, A, 09222910), relating to a method of suppressing vibrations due to axis interference in a multiaxial robot with a mechanism having spring elements such as speed reducers between electric motors of respective axes and robot arms. According to the invention disclosed in Japanese laid-open patent application No. Hei 9-222910, state observers associated with the axes of the multiaxial robot predict torsion angles between the electric motors and loads, and interfering forces are calculated using the predicted torsion angles. Based on the interfering forces, corrective torques are determined, added to the torques of the electric motors, and outputted.
In the control method disclosed in Japanese laid-open patent application No. Hei 9-222910, however, the values of the torsion angles predicted by the state observers are differentiated to calculate the corrective torques. Therefore, noise tends to be introduced into the corrective torques, causing the electric motors to produce high-frequency vibrations and large sounds in operation.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a robot control method to increase the path precision of a tool tip without causing vibrations produced by mechanical interference between axes and high-frequency vibrations of electric motors.
Another object of the present invention is to provide a robot control device to increase the path precision of a tool tip without causing vibrations produced by mechanical interference between axes and high-frequency vibrations of electric motors.
The first-mentioned object of the present invention can be achieved by a method of controlling, as an object to be controlled, a multiaxial robot including a mechanism which has spring elements between electric motors of respective axes and robot arms, comprising the steps of providing a pseudo-model of the object to be controlled and a feedback control system for the object to be controlled, calculating model motor position commands, model motor speed commands, and model feed-forward commands for the respective axes, using the pseudo-model, upon being supplied with position commands for the respective electric motors, determining interfering torques due to interference acting between the axes from the other axes, using the pseudo-model, and calculating model corrective torques to cancel the interfering torques, adding the model corrective torques to the model feed-forward commands to produce final model motor acceleration commands, and executing a feedback control process for the axes depending on the model motor position commands, the model motor speed commands, and the final model motor acceleration commands.
The other object of the present invention can be achieved by an apparatus for controlling a multiaxial robot including a mechanism which has spring elements between electric motors of respective axes and robot arms, comprising a model controller for being supplied with position commands for the respective electric motors and calculating model motor position commands, model motor speed commands, and model feed-forward commands for the respective axes, and feedback controllers for actuating and controlling the electric motors and the robot arms based on the commands outputted from the model controller, the model controller having corrective quantity calculators for determining interfering torques due to interference acting between the axes from the other axes and calculating model corrective torques to cancel the interfering torques, whereby the model controller outputs the model feed-forward commands with the model corrective torques added thereto.
For calculating corrective quantities in the present invention, interfering torques can be calculated from model torsion angles which are positional differences between model motors and model robot arms.
According to the present invention, an interfering force which a certain axis of the robot receives from another axis is determined as an interfering torque, and corrected by the model controller. Standard state quantities based on the corrective quantities (corrective torques) are supplied to the feedback controllers. Since the corrective quantities for canceling the interfering forces are calculated using quantities in a model, e.g., model torsion angles, no noise components are added to the corrective quantities even when differential calculations are performed. Therefore, high-frequency vibrations of the electric motors and sounds produced thereby during their operation are prevented from increasing, and the path precision of a robot tool is improved.
REFERENCES:
patent: 4786847 (1988-11-01), Daggett et al.
patent: 4829219 (1989-05-01), Penkar
patent: 4851748 (1989-07-01), Daggett et al.
patent: 4864204 (1989-09-01), Daggett et al.
patent: 4864206 (1989-09-01), Onaga et al.
patent: 4868474 (1989-09-01), Lancraft et al.
patent: 4962338 (1990-10-01), Daggett et al.
patent: 5319789 (1994-06-01), Ehlig et al.
Tsusaka et al., Development of a Fast Assembly Robot Arm with Joint Torque Sensory Feedback Control, 1995, IEEE, pp. 2230-2235.*
Wang et al., Experiments on the Position Control of a One-Link Flexible Robot Arm, 1989, IEEE, 373-377.
Kariyazaki Hirokazu
Ojima Masao
Tomisaki Hidenori
Cuchlinski Jr. William A.
Kabushiki Kaisha Yaskawa Denki
Marc McDieunel
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
LandOfFree
Robot control method and device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Robot control method and device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Robot control method and device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2521161