Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B19/00—Program-control systems
  • G05B19/02—Program-control systems electric
  • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form
  • G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J9/00—Program-controlled manipulators
  • B25J9/16—Program controls
  • B25J9/1628—Program controls characterised by the control loop
  • B25J9/1633—Program controls characterised by the control loop compliant, force, torque control, e.g. combined with position control
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/43—Speed, acceleration, deceleration control ADC
  • G05B2219/43201—Limit speed to allowable speed for all axis

Definitions

• This invention relates to position controls.
• Electromechanical position controllers use motors have an inherent velocity limit in the back EMF of the motor verses the supply voltage to the system. As the supply voltage varies the velocity limit of the system varies. Hydraulic systems are limited by the pump characteristic and other loads on the hydraulic pump when the actuator is operated. In a single gimbal control moment gyroscope (CMG) controlled satellite application, the velocity limit becomes the available angular momentum from the CMG array.
• CMG gimbal control moment gyroscope
• the problem with a velocity limited force limited system is that there is inconsistent performance when the velocity limit changes. Using a linear control results in good performance with a low velocity limit but a system that over shoots if there are high velocity limit. Conversely, good performance with a high velocity limit and produces a long settling time with a smaller velocity limit.
• Fig. 1 exemplifies the prior art and the limit problem.
• a controller 10 provides a position command X c which is summed with the velocity and position of an object or "mass" 12.
• a force limited actuator 14, such as a CMG is controlled by the position error 16 and moves the mass 12.
• the function 18 represents the inherent actuator force limit as a function of input position error at 16.
• the function 18 output is effectively summed with a velocity limit VL from a velocity limit 11 for the actuator, such as a power supply limit or CMG angular momentum saturation.
• the actuator has inherent feedback and transfer characteristics 14a-b, in addition to the force limitation that is represented by transfer function 18.
• FIG. 1 is a functional block diagram of a prior art control system.
• Fig. 2 is a functional block diagram of a control system that employs the present invention.
• a velocity error is compared to a limit that is a nonlinear function of the position error. If the position error is greater than the velocity limit, the velocity limit is used for the velocity command; otherwise the position error is used. The velocity command is compared with the velocity feedback to generate the velocity error.
• the second commanded velocity in axis is applied to a non-linear velocity limit using the following function:
• a benefit of the invention is that any transient settles in the same way, i.e., has the same overshoot, undershoot.
• Another benefit is that the performance is independent of the actuator (plant) velocity limit.
• An actuator's velocity limits do not have to be known.
• n Using the "n" axis function as the basis for the velocity limit for each axis, a nonlinear control can be built based on ellipsoidal torque and velocity limits in an n- dimensional control, such as a CMG set in a satellite.
• Fig. 2 shows a single axis control; that is, the mass moves in a straight line and neither it or the actuator 18 are rotating. It receives the position signal X c which is summed with object position at 22, the position error being applied to a gain 24, producing a velocity output at 26 that is applied to a non-linear limitation function 28 for the one or single axis based on the position error.
• the velocity command output at 30 is summed at 32 with the mass velocity, and the error is applied to a gain 34 to produce a force with a saturation that is applied to the actuator 18.
• equations 1 and 2 which define the function 28 for a "single axis" control problem.
• the desire is to bring the error to zero in each of the axes at the same time. This means that the deceleration time for each axis needs to be the same.
• Equation 13 produces a non-linear velocity limit as a function of position and maximum acceleration in three coupled axis where the only variable is position (e.g., position of one axis of the satellite)
• position e.g., position of one axis of the satellite
• equation 22 for function 28 based as the basis for the velocity limit for the value 30 for each axis when the velocity error exceeds a certain maximum plus/minus value
• a nonlinear control can be built based on ellipsoidal torque and velocity limits, where the velocity limit does not to be known be the control.

Landscapes

• Engineering & Computer Science (AREA)
• Robotics (AREA)
• Mechanical Engineering (AREA)
• Human Computer Interaction (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Automation & Control Theory (AREA)
• Control Of Position Or Direction (AREA)
• Feedback Control In General (AREA)
• Control Of Electric Motors In General (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (6)

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Family Cites Families (6)

• 1999
  • 1999-05-20 US US09/315,563 patent/US6477433B1/en not_active Expired - Fee Related
  • 1999-06-04 DE DE69902590T patent/DE69902590T2/de not_active Expired - Fee Related
  • 1999-06-04 EP EP99948032A patent/EP1086409B1/en not_active Expired - Lifetime
  • 1999-06-04 RU RU2000132962/09A patent/RU2000132962A/ru not_active Application Discontinuation
  • 1999-06-04 WO PCT/US1999/012577 patent/WO1999066375A2/en not_active Ceased
  • 1999-06-04 JP JP2000555134A patent/JP2002518724A/ja active Pending

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