my Think

Control systems are designed for specific tasks
Need Performance specifications:

• Accuracy,
• Stability,
• Speed of response.

Specifications may be changed in the process design (can not be achieved, not economical). Keep in priority order specification.

Conventional approaches to design:

• Performance Specifications:

Time domain: (tn,% Mp, ts)
Frequency domain: phase margin,

gain margin, bandwidth.

• Tool design:

Time domain: Root Locus
Frequency domain: Bode Plot, Nyquist, and so on.

• Limited to the SISO, linear time invariant.
• The specifications tested are met through gains adjustment by trial and error method.

•  Not always successful since plants can not changed.

• Need to re-design: the compensation. 

Series and Parallel Compensation











Selection Criteria:

• Properties of signals in the system
• Availability of components
• Economic factors
• Experience Designer
• Power level at some point

Compensation Series: 

• More simple.
• Need additional gain amplifier to strengthen and / or create isolation.
• Placed at the point with the lowest power path forward (to reduce power dissipation).   

Parallel Compensation:

Number of fewer components, as occurs in transfer of energy from higher level to a level more low.

 Compensators Lead, Lag and Lag-lead

• Lead: phase precedes the input output
• Lag: backward output from the input phase
• Lag-lead: lag phase occurs at low frequency, phase lead occurs at high frequency.

 The realization of compensators

• Active Electronic Devices (op amp)
• Passive Device: Electric (RC network + Amplifier)
• Mechanics
• Pneumatic
• Hydraulik
• Combination