Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1986-02-21
1987-11-10
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
364513, G05B 1942
Patent
active
047059990
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling a first arm and a second arm of an articulated robot having two pivotally connected arms.
Recently, by using a microprocessor, the control method for an industrial robot has changed to a digitized system to permit improved operating characteristics and velocity control of a robot arm based on a memorized cam curve whereby velocity instructions may be executed.
More specifically, the cam curve (S curve) having a relationship between time and a displacement amount, as shown in FIG. 1, is digitized and memorized as an S-table beforehand in a memory device and a desired displacement amount is derived one by one based on the cam curve at an operational time and a positional deviation against a present position and is supplied as a velocity instruction to a motor which drives each arm. In order to make the first arm and the second arm start simultaneously and to stop simultaneously, an instruction value derived from the S table is multiplied by a ratio of a displacement pulse amount for a first motor to a displacement pulse amount for a second motor, thereby producing an actual issued desired displacement amount.
As another method for supplying the velocity instruction to each motor, a hybrid control method is known that the cam curve having a relationship between the time and the velocity, as shown in FIGS. 2 and 3, is digitized and memorized in the memory device, and a velocity is derived one by one based on the cam curve at the operational time, and the control for the displacement amount is executed separately based on an integrated value of the issued velocity instruction, or another method using a cam curve having a relationship between the displacement amount and the velocity, as shown in FIGS. 4 and 5, is known.
Essentially, the articulated robot has characteristics such that the moment of inertia changes principally as a function of an angle of the second arm, and a centrifugal force or Coriolis force changes principally as a function of the angle of the second arm and the movement of the first arm and the second arm. Therefore, the load torque presented to a motor or a speed reducer changes largely as a function of the angle of the second arm and the movement of the first and second arms.
However, in the above-mentioned conventional methods, uniform acceleration and deceleration are executed without specifically considering the variation of the load and, therefore, the load torque under the severest conditions should not exceed a tolerance limit; that is, the uniform acceleration and deceleration are executed against an idle operation and the uniform acceleration and the uniform deceleration are substantial obstacles against a shortening of the time to effect a displacement from one point to another.
SUMMARY OF THE INVENTION
The first object of the present invention is to offer a method for controlling an articulated robot, which can control each arm in a manner such that the shortest transfer time is realized under such conditions that the capabilities of a motor and a driving circuit are best utilized and the torque load of the speed reducer does not exceed its tolerance limit.
Another object of the present invention is to offer a method for controlling an articulated robot, which can substantially shorten the transfer time for a displacement from one point to another in comparison with the conventional method which fixes the acceleration and deceleration time.
The above-mentioned object of the present invention is achieved by a method for controlling an articulated robot, wherein control is effected by supplying an angular velocity instruction to the respective motors of the first arm and the second arm, in an articulated robot comprising a first arm supported rotatablly by a main body via a first articulated joint, a second arm supported rotatablly by the first arm via a second articulated joint, a first motor and a second motor, or alternatively, a first motor and a first speed reducer and a second motor and
REFERENCES:
patent: 4534006 (1985-08-01), Minucciani
Nagano Hiroyuki
Soji Kazuo
Bergmann Saul M.
Matsushita Electric - Industrial Co., Ltd.
Shoop Jr. William M.
LandOfFree
Method for controlling an articulated robot does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for controlling an articulated robot, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for controlling an articulated robot will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1070034