Feedback control system
A closed loop control system for controlling an actuator operating on a moveable member, includes a control device controlling operation of the actuator, a sensor responsive to a condition such as loading of the moveable member as it is moved by the actuator and adapted to generate a corresponding feedback control signal S L , and a damping device having a damping effect on the response of the actuator to the feedback control signal, the damping effect being varied in accordance with the movement of the moveable member so as to vary the response of the actuator. The damping effect is increased in the region of stationary states to render the system more stable, and reduced therebetween to make the system more responsive at increased speeds, and thereby more conformal to a required performance profile. The position or velocity of the moveable member can be used to control the damping effect, or a timer can be used to control the damping effect.
1. Test apparatus for testing a moveable member subject to a load in use, the apparatus comprising:
a load actuator to apply a load to the moveable member,
a load controller that controls operation of the load actuator so as to apply a predetermined load to the moveable member as it is moved, and
a damping controller that is responsive to a condition of the moveable member as it is moved and that generates a corresponding damping signal to control the damping effect of the load actuator on movement of the moveable member,
wherein
the load controller includes a load sensor that senses the load applied by the load actuator to the moveable member and generates a load feedback signal, a load command generator that generates a load command signal dependent upon the position of the moveable member, and a comparator that combines the load feedback signal and load command signal to generate a load control signal that determines the load applied by the load actuator.
2. Apparatus as claimed in claim 1 wherein the damping controller includes a position or velocity sensor adapted to sense the position or velocity of the moveable member and to generate a corresponding position or velocity signal that controls generation of the damping signal.
3. Apparatus as claimed in claim 2 wherein the moveable member is moved from a start position, and the position or velocity sensor detects a first position or velocity level after the start position and controls generation of the damping signal at said first position or velocity level to reduce the damping effect of the load actuator.
4. Apparatus as claimed in claim 2 wherein the moveable member is moved to an end position, and the position or velocity sensor detects a second position or velocity level before the end position and controls generation of the damping signal at said second position or velocity level to increase the damping effect of the load actuator.
5. Apparatus as claimed in claim 1 wherein the damping controller comprises a damping signal generator that generates a damping signal in accordance with movement of the moveable member and which is combined with the load command signal in the comparator.
6. Apparatus as claimed in claim 1 wherein the damping controller includes a position sensor that generates a position signal in accordance with the position of the moveable member and that serves to synchronise generation of the damping signal with movement of the moveable member.
7. Apparatus as claimed in claim 1 including a primary actuator that serves to move the moveable member.