General purpose position control system having recursive profile generator

• US 5,770,829 A
• Filed: 06/09/1997
• Issued: 06/23/1998
• Est. Priority Date: 06/09/1997
• Status: Expired due to Fees

• Current Assignee: Oriental Motor Boston Technology Group Incorporated
• Original Assignee: Seiberco Incorporated
• Inventors: Katz, Stanley Maurice, O'Neill, Francis Brian
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/871,370
• Time in Patent Office: 379 Days
• Field of Search: 318/560, 318/567, 318/568.1, 318/568.11, 318/568.17, 318/568.18, 318/671
• US Class Current: 318/560
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/43084 Acceleration deceleration circuit implemented in software, algorithm
• CPC Class Codes: G05B 2219/43182 Speed control with feedback and as reference the programmed value

Abstract

The recursive profile generator of a general purpose position control system relies only upon current state and target state information in generating the path of movement for the armature of the servomotor. The profile generator employs a convergent algorithm for calculating the acceleration necessary to reach each control point or target position. By ignoring previous state information, the profile generator makes the use of reduced computing power possible and readily accommodates changing target state conditions.

Claims

1. A method for controlling the motion of an electric servomotor having an armature with armature-position control capability, utilizing an operating system for supplying electric current to the servomotor, the system being iteratively controlled to have a cycle, with a delay time of value t_D, for effecting movement of the armature to desired positions, and including a motion generation component for defining an armature travel path comprised of said desired positions taken cumulatively;

characterized in that the motion generation component carries out the following steps during each cycle of the operating system;

(a) receives current state signals that are representative of the current position "P" and the current velocity "V" of the armature, and the current time "T";

(b) receives target state signals that are representative of a desired armature position "P_T ", a desired armature velocity "V_T ", and a target time "T_T " for achieving said desired position and desired velocity;

(c) calculates the remaining armature travel distance "D" required to achieve said desired position, equal to P_T -P, using said current and target state signals;

(d) calculates the remaining time "t", equal to T_T -T, using said current and target state signals;

(e) calculates the acceleration "a" required to achieve the state represented by said target state signals, where "a" is equal to the quantity (6D/t-2V_T -4V)/t;

(f) calculates the sum of said current velocity V, added to the product of said acceleration a and said delay time t_D, to determine a commanded velocity "V_NEW ";

(g) calculates the sum of said current position P, added to the product of said commanded velocity V_NEW and said delay time t_D, to determine a commanded position "P_NEW "; and

(h) generates signals indicative of said commanded velocity and said commanded position for use in said operating system for supplying electric current to effect movement of said motor armature;

said motion generation component functioning without utilizing any signal that is representative of any prior state of said armature, and without making inquiry as to changes in the state of said armature from a state prior to the current state.

2. The method of claim 1 wherein said motion generation component carries out the additional step of determining whether said operating system is configured for open loop or closed loop operation.

3. The method of claim 2 wherein said motion generation component determines that said operating system is configured for closed loop operation, and wherein said current state signals are representative of the actual state of the servomotor armature.

4. The method of claim 2 wherein said motion generation component determines that said operating system is configured for open loop operation, and wherein said current state signals are representative of the immediately prior commanded state of the servomotor armature.

5. A servomotor motion control system comprising:

an electric motor having an armature, with armature-position control capability; and

an operating system for supplying electric current to said motor, iteratively controlled to have a cycle with a delay time of value t_D, for effecting movement of said armature to desired positions, said operating system including a motion generation component that is constructed to carry out the following steps during each cycle of said operating system, and thereby to define an armature travel path comprised of said desired positions taken cumulatively;

(a) receiving current state signals that are representative of the current position "P" and the current velocity "V" of said armature, and the current time "T";

(b) receiving target state signals that are representative of a desired armature position "P_T ", a desired armature velocity "V_T ", and a target time "T_T " for achieving said desired position and desired velocity;

(c) calculating the remaining armature travel distance "D" required to achieve said desired position, equal to P_T -P, using said current and target state signals;

(d) calculating the remaining time "t", equal to T_T -T, using said current and target state signals;

(e) calculating the acceleration "a" required to achieve the state represented by said target state signals, where "a" is equal to the quantity (6D/t-2V_T -4V)/t;

(f) calculating the sum of said current velocity V, added to the product of said acceleration a and said delay time t_D, to determine a commanded velocity "V_NEW ";

(g) calculating the sum of said current position P, added to the product of said commanded velocity V_NEW and said delay time t_D, to determine a commanded position "P_NEW "; and

(h) generating signals indicative of said commanded velocity and said commanded position for use in said operating system for supplying electric current to effect movement of said motor armature, said motion generation component being devoid of a capability of utilizing any signal that is representative of any prior state of said armature, and being devoid of a capability of inquiry as to changes in the state of said armature from a state prior to the current state.

6. The system of claim 5 additionally including a supervisory controller component and a position feedback component, said supervisory controller component and said feedback component being operatively connected for providing such current state signals to said motion generation component in open and closed loop modes of operation, respectively, said motion generation component being constructed to determine whether said system is configured for open loop or closed loop operation, and to accordingly receive said current state signals from said supervisory controller component or said feedback component, respectively.

7. The system of claim 6 additionally including a position controller component and a motor driver component, said position controller and motor driver components being operatively interconnected to one another, and to said motion generation component and said electric motor, for supplying electric current to said motor for generating torque values therein appropriate for moving said armature to said commanded position at said commanded velocity.