This chapter presents development and experimental evaluation of low-cost embedded system for control of liquid level in a model of tank. The plant is a physical laboratory model of water tank produced by Lucas Nülle Company [134]. The liquid level is controlled in wide range by designed and, H_∞ controllers. The control algorithms are implemented in low-cost control kit Arduino Mega 2560 [135]. Software in MATLAB/Simulink® environment is developed for generation of control code. Some additional simple hardware devices are developed too. These devices provide appropriate voltage level of analogue signals which are exchanging between physical model of tank and control kit. Controllers are designed on the basis of the linear discrete-time black-box model derived from experimental data by one of the identification techniques described in Appendix D. The main advantage of this technique is that we obtain low-order models of plant and noise. The noise model is used to design appropriate Kalman filter that reduces significantly the sensitivity of control signal to the noise, which is very important for correct exploitation of the actuator. Results from simulation of the closed-loop system as well as experimental results obtained from real-time implementation of designed controllers are given. They confirm embedded control system performance in the whole working range.

Chapter Contents:

• 5.1 Hardware configuration of embedded control system
• 5.1.1 Water tank
• 5.1.2 ARDUINO MEGA 2560
• 5.1.3 Voltage divider
• 5.1.4 Relay block
• 5.2 Plant identification
• 5.3 LQR and LQG controllers design
• 5.4 H∞ Controller design
• 5.5 Experimental evaluation
• 5.6 Notes and references

Inspec keywords: discrete time systems; embedded systems; level control; closed loop systems; water storage; H∞ control; identification; Kalman filters; tanks (containers); control system synthesis; linear systems

Other keywords: closed-loop system simulation; tank physical model; low-order models; hardware devices; Matlab-Simulink environment; low-cost embedded system; noise model; liquid level control; H_∞ controllers; water tank; actuator; analogue signals; linear discrete-time black-box model; low-cost control kit Arduino Mega 2560; control signal sensitivity; Kalman filter design; physical laboratory model; controller design; embedded control; identification techniques; control code generation

Subjects: Linear control systems; Discrete control systems; Simulation, modelling and identification; Control system analysis and synthesis methods; Optimal control; Level, flow and volume control; Signal processing theory