FPC - Control of Electrohydraulic Systems
Brief description
Delegates taking the FPC course will attend the C module for the first 2 days and then concentrate on more advanced modelling and control strategies for electrohydraulic systems for the remaining time. At the end, participants should be able to predict the behaviour of electrohydraulic systems, determine a system’s frequency response and stability characteristics, and improve the steady state and dynamic response using appropriate compensation techniques.
Who should attend
The course is suitable for engineering professionals, system and control designers, software developers, and graduates. It is assumed that the participants have basic knowledge of mechatronic systems involving in particular electrohydraulic and electromagnetic components. For engineers new to this field, we recommend our introductory courses for hydraulics and electrical drives. A solid mathematical knowledge is needed.
Course objectives
Upon completion, participants should be able to do the following:
- Appreciate the need for feedback control in practical mechatronic systems.
- Derive dynamical models and represent them in block diagram notation.
- Analyse stability and performance of systems in the time and frequency domain using step and impulse responses, root-locus, Bode and Nyquist diagrams.
- Know the basic principles and applications of open- and closed loop control strategies; design and tune PID controllers.
- Appreciate the differences between analog and digital control.
- Perform system identification and verify models.
- Be aware of measurement errors and noise in real systems, and their effect on controller performance.
- Utilise rapid development tools for system analysis and controller design.
- Design position and force controllers for electrohydraulic systems.
- Analyse the dynamical characteristics of hydraulic valves and actuators, and derive mathematical models of hydraulic systems in the time and frequency domain.
- Know the principles and limitations of hydromechanical position control.
- Have a working knowledge of valve drive controllers and amplifier hardware.
Course contents
Controller design case studies
- Basic feedback control principles.
- Time response characteristics - rise time, settling time, overshoot.
- Steady state errors.
- Effects of sensor dynamics and measurement errors.
Block diagrams
- Series, parallel, and feedback connections.
- Deriving closed loop transfer functions.
- Single-input single-output and multi-input multi-output (MIMO) systems.
PID control
- General closed loop controller structure - forward path, feedback path, and demand compensators.
- Effects of P, I, D gains in the time domain and their influence on performance and steady state errors.
- Analog and digital implementation.
System modelling
- Basics of differential equations - behaviour of first and second order systems.
- Transfer functions and Laplace notation.
- Effects of delays and system nonlinearities.
Frequency response and stability
- Physical meaning of eigenfrequencies and eigenmodes.
- Open- and closed loop frequency responses; Nyquist plots.
- Root-locus analysis.
- Gain and phase margin, Nyquist stability criterion.
System identification
- Obtaining experimental frequency responses - excitation methods, data sampling, filtering, FFT.
- Representation in Bode diagram.
- Estimation algorithms, coherence, transfer function fit.
Model based controller tuning
- General controller design process.
- Influence of P, I, D gains on the system's frequency response.
- Meeting stability and performance specifications.
Practical controller implementation
- Low-pass filtering to rduce noise.
- Discrete-time signals, aliasing and the sampling theorem.
- Controller hardware and software development environments.
Dynamics of a valve-operated actuator
- Valve spool dynamics, orifice equations, actuator flow equations, force balance.
- Linearisation with small perturbation method.
- Influence of under- and over lapped spools, and unequal actuator volumes.
- Time and frequency responses, resonance frequencies, damping.
Hydromechanical and electrohydraulic position control
- Mechanical and electrical feedback servo systems.
- Position and force control.
- Analysis of open and closed loop frequency responses, stability.
Valve drive amplifiers and controllers
- Voltage and current amplifiers.
- Amplifier dynamics.
- Control units, rapid-prototyping hardware.
Controller design for electrohydraulic servo systems
- Limitations of PID controllers.
- Pressure and acceleration feedback, notch filters.
- Sensor dynamics, minimising sensitivity to measurement errors.
Workshops and laboratory sessions
- PID tuning demos
- System modelling tutorial
- Controller design tutorial
- Real time controller implementation lab
- Hydraulic system modelling tutorial
- Servo valve control circuits lab
- Frequency response testing lab
- Control system stability lab
- Controller design exercise
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This course is run in conjunction with the Institution of Mechanical Engineers. |