Mechanical Engineering - Control and Actuating Devices for Mechanical Systems

Oral exam

O RAL QUESTIONS OF CADMS, 23 RD JA N UA RY Braghin – Control position of hydraulics actuators. – Noise. – Hydraulic actuators for force control: best controller. – PID Tuning. – AC motor model. – P VS PD. – Braghin asked me orally why we have distri- bution line in pneumatics and not in hydrau- lics. – Hydraulic actuator model. – Laplace transform: definition, condition of existence, main properties and basic func- tions transform. – Stability of 1 d.o.f. system. – How to deal with noise and disturbances. – Best controller for velocity with a DC motor. – Rules for root locus. Assistants – Hydraulic VS pneumatic. – Cauchy’s principle of argument. – Permanent magnet DC motor model. – Advantages of feedback and feedforward. – Stability of 2 d.o.f. in presence of positional force fields (conservative and not conserva- tive). – Co-located and non-co-located controllers. – Effect of transducer delay. – Best controller for position in DC motor. – Additional question: noise and disturbances TF. – Best controller to control the force in a hy- draulic actuator. – Lyapunov stability. – Comment the question about relative stabil- ity and explain the difference between a suf- ficient condition (if it’s not verified nothing can be said) and necessary one (if it’s not ver- ified, then the sentence it’s not valid). – What’s important in pole placement: poles velocity which implies more power and more exposure to noise, mainly manage the behav- iour of the slow poles because they affect most the dynamic response and so the tran- sient.