Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1989-03-23
1990-09-11
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
31856822, 318632, 901 9, 364513, G05B 1942
Patent
active
049565940
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a robot control method capable of making a robot effect various operations in accordance with optimum control conditions.
(b) Description of the Related Art
In a conventional robot having servomotors for actuating various axes of the robot and servo systems for driving the servomotors, the response characteristics of the servo systems to their respective inputs and the servo gains for determining control conditions of the robot, e.g., gains in the proportional, integrating and differentiating elements involved in the servo systems, are set such that the response characteristics of the servo systems may be optimum when maximum load is applied on the servomotors. Thus, the conventional robot is controlled in accordance with control conditions which are unchangeable.
Meanwhile, the robot is required to make various operations, and the load applied on the servomotors of the robot varies depending on kinds of the operations of the robot. Therefore, if the control conditions of the robot are determined so as to be best suited to the maximum load, as mentioned above, excessive driving force can be supplied to the servomotors in ordinary states (i.e., when the maximum load is not applied on the robot). The tendency is particularly conspicuous in the case of a direct drive type robot. Thus, in the conventional robot, the response characteristics of the servo systems and, in turn, the control conditions of the robot are not in conformity to load conditions other than the maximum load condition. As a result, disadvantages arise, for example, in that the outputs of the servo systems overshoot the inputs thereto and oscillate, which causes vibration of the robot.
SUMMARY OF THE INVENTION
The object of the invention is to provide a robot control method capable of making a robot effect various operations, which require different load conditions, in accordance with optimum control conditions.
To achieve the above-mentioned object, the robot control method according to the invention comprises the steps of: (a) setting and storing beforehand load conditions for various operations of the robot; (b) reading a program including operation commands for instructing a series of operations to be made by the robot and load condition commands each representing a load condition of a corresponding operation in the series of operations and described in relation to the corresponding operation; (c) reading one of the load conditions stored in the step (a) which corresponds to a read-out load condition command when the load condition commands are individually read from the program in the step (b), and determining a desired control condition on the basis of the load condition thus read out; and (d) controlling the drive of the robot in accordance with the desired control condition determined in the step (c).
An advantage of the present invention is that, since the robot is controlled according to an optimum control condition based on the load condition which is set for an operation to be executed by the robot, no excessive driving force is supplied to the servomotors which actuate the individual axes of the robot, and vibration of the robot is prevented, whereby the robot can be controlled under the most desirable conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram schematically illustrating a robot and its peripheral elements to which a robot control method according to one embodiment of the invention is applied;
FIG. 2 is a diagram showing a load condition table used in the method of the present invention; and
FIG. 3 is a block diagram showing the internal arrangement of a servo circuit in FIG. 1 in terms of transfer functions.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, reference numeral 1 denotes a numerical control system serving as a control system for controlling a robot, 2 denotes a body of the robot, 3 denotes a work section on which the robot body 2 works, and 4 denotes a relay unit for controlling
REFERENCES:
patent: 4860215 (1989-08-01), Seraji
patent: 4873476 (1989-10-01), Kurakabe et al.
Ishikawa Haruyuki
Iwamoto Takashi
Mizuno Toru
Bergmann Saul M.
Fanuc Ltd.
Shoop Jr. William M.
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