Position control system for a closed loop type numerical-controlled machine tool
AssigneeFujitsu Fanuc Limited
InventorMitsuo Kurakake
Life of this patent
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Abstract
In a closed loop type numerical-controlled machine tool in which position control of a mechanical moving part is performed in accordance with a position error variable obtained by making a comparison between commanded positional information and detected positional information from a position detector mounted on the mechanical moving part, deteriorated performance resulting from the inclusion of the mechanical moving part in the closed loop is improved by using correcting means incorporated in the numerical-controlled machine tool.
Claims13
A position control system for a closed loop numerical-controlled machine tool in which the position of a mechanical moving part is controlled according to a position command, said system comprising
- a position detector mounted for detecting the position of the mechanical moving part,
- means for determining a positioning error signal by making a comparison between the position command and the detected position from said position detector, and
- correcting means for reducing the positioning error signal resulting from the inclusion of the mechanical moving part in the closed loop, said correcting means comprising a compensator included in the closed loop, said compensator comprising
- a processor,
- means for increasing the break angular frequency of said closed loop including the mechanical moving part, and for increasing the gain of the feedback of the closed loop in correspondence to the value of said positioning error signal in a stable region of the closed loop, said gain being usable for higher frequencies as a result of said increased break angular frequency of said closed loop including said compensator than for frequencies without said compensator.
In a closed loop system for positioning a moving part according to a commanded position, the mechanical portion of said system including said moving parts having a nonlinear element in its transfer function, said closed loop including
- a first adder having as one input said commanded position,
- a gain setting circuit, having as input the output of said adder,
- a velocity amplifier having as input the output of said gain setting circuit,
- a motor having as input the output of said velocity amplifier,
- mechanical linkage connecting said motor to said moving part,
- a position detector mounted to detect the position of said moving part, and
- said first adder comprising means for forming said output to be the difference between said commanded position and said detected position, the improvement comprising:
- said closed loop comprising a compensator connected between said first adder and said gain setting circuit, said compensator comprising means for increasing the break angular frequency of the transfer function of said closed loop without said compensator by varying said input to said gain setting circuit in correspondence with said output of said first adder, said compensator acting to increase said break angular frequency of the closed loop including the compensator when the break angular frequency .omega..sub.M of the transfer function of said mechanical linkage and said moving part is lower than the break angular frequency .omega..sub.V of the transfer function of the combination of the velocity amplifier and the motor, as a result of selecting the parameters of the compensator so that the characteristic equation of the closed loop including said compensator has selected characteristic roots larger than at least the smallest root of the characteristic equation of the closed loop without said compensator.
In a closed loop system for positioning a moving part according to a commanded position, the mechanical portion of said closed loop including said moving part having a nonlinear element in its transfer function, said closed loop including
- a first adder having as one input said commanded position,
- a gain setting circuit, having as input the output of said first adder,
- a velocity amplifier having as input the output of said gain setting circuit,
- a motor having as input the output of said velocity amplifier,
- mechanical linkage connecting said motor to said moving part,
- a position detector mounted to detect the position of said moving part, and
- said first adder comprising means for forming outputting the difference between said commanded position and said detected position, the improvement comprising:
- a simulator having as input said commanded position and means for computing by means of a processor an output comprising a simulated value of the position of the moving part, said computing of said simulated value taking account only of the linear portions of the response function of said closed loop,
- difference means for outputting a positioning error corresponding to the difference between said simulated value and said detected position, and
- means for adjusting the gain of said gain setting circuit in correspondence to said positioning error.
In a closed loop control system for positioning a moving part according to a commanded position, the mechanical portion of said closed loop including said moving part having a nonlinear element in its transfer function, said closed loop including
- a first adder having as one input said commanded position,
- a gain setting circuit, having as input the output of said first adder,
- a velocity amplifier having as input the output of said gain setting circuit,
- a motor having as input the output of said velocity amplifier,
- mechanical linkage connecting said motor to said moving part,
- a position detector mounted to detect the position of said moving part, and
- said first adder comprising means for forming said output to be the difference between said commanded position and said detected position, the improvement comprising:
- a simulator having as input said commanded position and means for computing by means of a processor an output comprising a simulated value of the position of the moving part, said computing of said simulated value accounting only for the linear portion of the response function of the portion of said closed loop including at least the velocity amplifier, motor and mechanical linkage, difference means for outputting a positioning error corresponding to the difference between said simulated value and said detected position to said gain setting circuit.
In a closed loop control system for positioning a moving part according to a commanded position, the mechanical portion of said closed loop including said moving part having a nonlinear element in its transfer function, said closed loop including
- a first adder having as one input said commanded position,
- a first gain setting circuit, having as input the output of said first adder,
- a velocity amplifier having as input the output of said first gain setting circuit,
- a motor having as input the output of said velocity amplifier,
- mechanical linkage connecting said motor to said moving part,
- a position detector mounted to detect the position of said moving part, and
- said first adder comprising means for forming said output to be the difference between said commanded position and said detected position, the improvement comprising:
- a simulator having as an input said commanded position and means for computing by means of a processor an output comprising a simulated value of the position of the moving part, and said computing of said simulated value accounting only for the linear portion of the open loop response function of said closed loop, difference means for outputting a positioning error corresponding to the difference between the simulated value and the detected position, a second gain setting circuit for receiving said difference between said simulated position value and said detected position and for outputting same in accord with a predetermined gain that is a predetermined increase in function of the absolute value of this latter difference, and further adder means for adding same to the difference from said first adder for input to said first gain setting circuit.
Dependencies are inferred from the claim text.