Method for controlling an articulated robot

• US 4,705,999 A
• Filed: 02/21/1986
• Issued: 11/10/1987
• Est. Priority Date: 04/27/1984
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Nagano, Hiroyuki, Soji, Kazuo
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): BERGMANN, SAUL
• Application Number:
  US06/827,932
• Time in Patent Office: 627 Days
• Field of Search: 318/568, 318/568 M, 364/513
• US Class Current: 318/568.18
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/41123 Correction inertia of servo
• CPC Class Codes: G05B 2219/43069 Measure acceleration, derive limit torque, adapt acceleration
• CPC Class Codes: G05B 2219/45083 Manipulators, robot

Abstract

A method for controlling a first arm (11) and a second arm (12) in an articulated robot comprising said first arm (11) supported rotatably by a main body (1) via a first articulated joint and said second arm (12) supported rotatably by said first arm (11) via a second articulated joint.

When a top of said second arm (12) moves from a certain starting point P_i to an end point P_i+1, the angular velocity curve during acceleration and deceleration is determined based on the positional data of the points P_i, P_i+1 in a manner such that the acceleration time and the deceleration time become shortest under such conditions that torques impressed on the motor (13), (14) and the speed reducer (15), (16) do not exceed an upper torque tolerance limit, respectively.

By such method, the transfer time can be shortened substantially and reasonably in comparison with the conventional method in which the acceleration and deceleration times are fixed.

Claims

1. A method for controlling an articulated robot of the type which comprises a first arm supported rotatably from a main body via a first articulated joint, a second arm supported rotatably from said first arm via a second articulated joint, and respective first and second motors coupled to said first and second articulated joints for rotating said first arm and said second arm, each of said first and second motors having a respective predetermined upper torque limit, wherein the displacement of said first arm and said second arm to displace the remote end of said second arm from an initial position P_i to a subsequent position P_i+1 is controlled by angular velocity instructions provided to said first and second motors to effect controlled acceleration and deceleration during displacement from the initial position P_i to the subsequent position P_i+1, said method comprising the steps of:

(a) storing a reference acceleration curve and a reference deceleration curve in a memory means by which velocity instruction values or desired displacement positional instruction values for said respective first and second motors are generated as a function of time or a displacement amount;

(b) reading in positional data for the initial position P_i and the subsequent position P_i+1 to which the remote end of the second arm is to be displaced;

(c) varying an acceleration time or a displacement amount to obtain an acceleration value as a function of said stored reference curve information for acceleration of the remote end of said second arm from position P_i to position P_i+1 ;

(d) calculating the torque load of said first motor and said second motor for acceleration of the remote end of said second arm from said initial position P_i to said subsequent position P_i+1 for the obtained acceleration value;

(e) repeating said varying step (c) and calculating step (d) until the calculated torque load for each of said first and second motors is below its predetermined upper torque limit and the calculated torque load for at least one of said first and second motors if at a maximum value under its predetermined upper torque limit;

(f) varying a deceleration time or a displacement amount to obtain an deceleration value as a function of said stored reference curve information for deceleration of the remote end of said second arm from position P_i to position P_i+1 ;

(g) calculating the torque load of said first motor and said second motor for deceleration of the remote end of said second arm from said initial position P_i to said subsequent position P_i+1 for the obtained deceleration value;

(h) repeating said varying step (f) and calculating step (g) until the calculated torque load for each of said first and second motors is below its predetermined upper torque limit and the calculated torque load for at least one of said first and second motors is at a maximum value under its predetermined upper torque limit;

(i) using said obtained acceleration time or said displacement amount during acceleration as a reference for said stored reference acceleration curve and issuing a velocity instruction value or a desired displacement positional instruction for the acceleration portion of the displacement of the remote end of said second arm; and

(j) using said obtained deceleration time or said displacement amount during deceleration as a reference for said stored reference deceleration curve and issuing a velocity instruction value or desired displacement positional instruction for the deceleration portion of the displacement of the remote end of said second arm.

2. A method for controlling an articulated robot of the type which comprises a first arm supported rotatably from a main body via a first articulated joint, a second arm supported rotatably from said first arm via a second articulated joint, and respective first and second motors coupled to said first and second articulated joints for rotating said first arm and said second arm, each of said first and second motors having a respective predetermined upper torque limit, wherein the displacement of said first arm and said second arm to displace the remote end of said second arm from an initial position P_i to a subsequent position P_i+1 is controlled by angular velocity instructions provided to said first and second motors to effect controlled acceleration and deceleration during displacement from the initial position P_i to the subsequent position P_i+1, said method comprising the steps of:

storing a reference acceleration curve and a reference deceleration curve in a memory device by which velocity instruction values or desired displacement positional instruction values are generated as a function of time or a displacement amount;

storing discrete values of factors which affect torque load of said first and second motors as a function of positional data for a displacement starting point and a displacement ending point;

calculating combination-values for all combinations of said discrete value parameters for acceleration times or the displacement amounts during acceleration, the deceleration times or the displacement amounts during deceleration which combination-values make said load torques of said first motor and said second motor below their respective predetermined upper torque limit and the torque load for at least one of said first and second motors at a maximum value under its predetermined upper torque limit;

memorizing the calculated combination-values in a memory device corresponding to said combinations of said discrete value parameters;

reading in positional data for an initial position P_i and a subsequent position P_i+1 ;

calculating factors used for said discrete value parameters from positional data for the initial position P_i and a subsequent position P_i+1 ;

comparing said factors calculated value with said stored discrete value parameters and obtaining the acceleration time or the displacement amount during acceleration and the deceleration time or the displacement amount during deceleration, which correspond to the nearest discrete value parameters;

using said acceleration time or said displacement amount during said acceleration obtained by said comparing step as a reference value for said reference acceleration curve and issuing velocity instruction values or a desired displacement positional instruction during acceleration; and

using said deceleration time or said displacement amount during deceleration obtained by said comparing step as a reference for said reference deceleration curve and issuing velocity instructions value or a desired transfer positional instruction in the deceleration.

3. A method for controlling an articulated robot of the type which comprises a first arm supported rotatably from a main body via a first articulated joint, a second arm supported rotatably from said first arm via a second articulated joint, a first motor and a first speed reducer coupled to said first articulated joint and a second motor and second speed reducer connected to said second articulated joint for rotating said first arm and said second arm, said first motor and first speed reducer and said second motor and second speed reducer having respective predetermined upper torque limits, wherein the displacement of said first arm and said second arm to displace the remote end of said second arm from an initial position P_i to a subsequent position P_i+1 is controlled by angular velocity instructions provided to said first and second motors to effect controlled acceleration and deceleration during displacement from the initial position P_i to the subsequent position P_i+1, said method comprising the steps of:

(a) storing a reference acceleration curve and a reference deceleration curve in a memory means by which velocity instruction values or desired displacement positional instruction values for said respective first and second motors are generated as a function of time or a displacement amount;

(b) reading in positional data for the initial position P_i and the subsequent position P_i+1 to which the remote end of the second arm is to be displaced;

(c) varying an acceleration time or a displacement amount to obtain an acceleration value as a function of said stored reference curve information for acceleration of the remote end of said second arm from position P_i to position P_i+1 ;

(d) calculating the torque load of said first motor and said first speed reducer and said second motor and said second speed reducer for acceleration of the remote end of said second arm from said initial position P_i to said subsequent position P_i+1 for the obtained acceleration value;

(e) repeating said varying step (c) and calculating step (d) until the calculated torque load for each of said first motor and first speed reducer and said second motor and second speed reducer is below their respective predetermined upper torque limit and the calculated torque load for at least one of said first motor and first speed reducer said second motor and second speed reducer is at a maximum value under its predetermined upper torque limit;

(f) varying a deceleration time or a displacement amount to obtain an deceleration value as a function of said stored reference curve information for deceleration of the remote end of said second arm from position P_i to position P_i+1 ;

(g) calculating the torque load of said first motor and said first speed reducer and said second motor and speed reducer for deceleration of the remote end of said second arm from said initial position P_i to said subsequent position P_i+1 for the obtained deceleration value;

(h) repeating said varying step (f) and calculating step (g) until the calculated torque load for each of said first motor and first speed reducer and said second motor and second speed reducer is below their respective predetermined upper torque limit and the calculated torque load for at least one of said first motor and speed reducer and said second motor and second speed reducer is at a maximum value under its predetermined upper torque limit;

(i) using said obtained acceleration time or said displacement amount during acceleration as a reference for said stored reference acceleration curve and issuing a velocity instruction value or a desired displacement positional instruction for the acceleration portion of the displacement of the remote end of said second arm; and

(j) using said obtained deceleration time or said displacement amount during deceleration as a reference of said reference deceleration curve and issuing a velocity instruction value or desired displacement positional instruction for the deceleration portion of the displacement of the remote end of said second arm.

4. A method for controlling an articulated robot of the type which comprises a first arm supported rotatably from a main body via a first articulated joint, a second arm supported rotatably from said first arm via a second articulated joint, a first motor and a first speed reducer coupled to said first articulated joint and a second motor and second speed reducer connected to said second articulated joint for rotating said first arm and said second arm, said first motor and first speed reducer and said second motor and second speed reducer having respective predetermined upper torque limits, wherein the displacement of said first arm and said second arm to displace the remote end of said second arm from an initial position P_i to a subsequent position P_i+1 is controlled by angular velocity instructions provided to said first and second motors to effect controlled acceleration and deceleration during displacement from the initial position P_i to the subsequent position P_i+1, said method comprising the steps of:

storing a reference acceleration curve and a reference deceleration curve in a memory device by which velocity instruction values or desired displacement positional instruction values are generated as a function of time or a displacement amount;

storing discrete values of factors which affect torque load of said first motor and first speed reducer and said second motor second speed reducer as a function of positional data for a displacement starting point and a displacement ending point;

calculating combination-values for all combinations of said discrete value parameters for acceleration times or the displacement amounts during acceleration and the deceleration times or the displacement amounts during deceleration which combination-values make said load torques of said first motor and first speed reducer and said second motor and second speed reducer below their respective predetermined upper torque limit and the torque load for at least one of said first motor and first speed reducer and said second motor and second speed reducer at a maximum value under its respective predetermined upper torque limit;

memorizing the calculated combination-values in a memory device corresponding to said combinations of said discrete value parameters;

reading in positional data for an initial position P_i and a subsequent position P_i+1 ;

calculating factors used for said discrete value parameters from positional data for the initial position P_i and a subsequent position P_i+1 ;

comparing said factors calculated value with said stored discrete value parameters and obtaining the acceleration time or the displacement amount during acceleration and the deceleration time or the displacement amount during deceleration, which correspond to the nearest discrete value parameters;

using said acceleration time or said displacement amount during said acceleration obtained by said comparing step as a reference value for said reference acceleration curve and issuing velocity instruction values or a desired displacement positional instruction during acceleration; and

using said deceleration time or said displacement amount during deceleration obtained by said comparing step as a reference for said reference deceleration curve and issuing velocity instructions value or a desired transfer positional instruction in the deceleration.