Servo control system for movable body, and laser drilling machine
View Patent ↗A difference between each position command data outputted in a form of a step signal from a high-level controller and its corresponding detected position data of a movable body is integrated by an integral compensator to position the movable body. Assuming, for example, that the movable body is a steerable mirror, digital filters are arranged to compensate the value of an initial state of an angular displacement and the value of an initial state of an angular velocity, respectively, and respective impulse responses of the digital filters as additional input elements are added to an output terminal of the integral compensator. For higher effectiveness, internal state variables of the digital filters can desirably be cleared to zero whenever an angle (position) command data is received.
1. A servo control system for a steerable mirror secured on a drive shaft of a rotary actuator, said servo control system being provided with a feedback loop such that said steerable mirror is positioned in an angular position based on position command data, comprising:
an input means for inputting an input signal which is said position command data; and
an additional input means for inputting at least one additional input signal, which is other than said position command data, to said feedback loop, wherein said additional input means is designated to add zeros to a transfer function for a q-th initial state value x p 0 q so as to cancel out poles of said transfer function, which poles are inherent in said feedback loop, in said transfer function for said initial state value x p 0 g of said feedback loop at a time at which said position command data has been received,
wherein said zeros are roots of the equation N pq (z)d q (z)+N u (z)n q (z)=0, where N pq (z) is the q-th element of the 1×m high-order polynomial matrix (1≦q≦m) of the transfer function of said feedback loop, d q (z) is the denominator of the transfer function of a digital filter for the q-th initial state value x x0q , N u (z) is the numerator of the transfer function for said additional input means, n q (z) is the numerator of the transfer function of said digital filter for the q-th initial state value X p0q , and
wherein said poles are roots of the equation D(z)=0, where D(z) is the denominator of the transfer function of said feedback loop, which poles are relating to the first-order torsional vibration mode of said drive shaft.
2. A servo control system according to claim 1 , wherein said additional input mean comprises at least one digital filter for being inputted with an impulse signal, which is equivalent to said state value at said time at which said position command data has been received, as an input signal; and at said time at which said position command data has been received, a state variable inside said digital filter is cleared to zero.
3. A servo control system according to claim 1 , wherein said position command data is a data in a form of a step signal.