Embedded Lab

The embedded control systems laboratory experiments and projects aim to address following issues:

  1. Identifying the transfer function of the system.
  2. Selection of sampling time for sensors and actuators.
  3. Deciding loop time based on sampling rates of actuator(s) and sensor(s).
  4. Discretizing the transfer function.
  5. Tuning the PID parameters.
  6. Selection of quantization levels for sensor inputs.
  7. Justifying the (in)stability of the system by considering the feasible sampling time.
  8. The output from the embedded controller is interfaced with DAC using multiple digital output ports. This interface is then modified to work with a single digital output port using PWM generation. The PWM frequency and duty cycles are selected based on the plant requirements.
  9. Parallel interfacing of encoders and motors using FPGA.
  10. Synchronisation of two motors using FPGA, microcontroller and embedded linux (giving flavour of different embedded platforms).
  11. Various advantages and limitations of micocontroller, FPGA and embedded linux platforms are demonstrated.

Following problems and corresponding setups are considered for providing hands-on exposure in embedded control laboratory:

The second order RC circuit with series resistors and parallel capacitors is considered as plant. The output voltage is controlled by varying the input voltage. This circuit configuration can be controlled through the PWM signals as it also acts as a low pass filter. The RC values are chosen such that the system is an over-damped without any controller. The circuit is controlled to achieve under-damped, critically-damped and over-damped responses by designing PID controllers.

The dual arm balancing system is the basis of a Quad rotor, and is thus a guideline and a starting point to building UAV’s. The setup prepared by students, as part of a mini project comprises of two motors with propellers. These motors are mounted with vertical axis at the ends of a horizontal beam. Controlling the thrusts provided by these motor-propeller systems controls the beam angle.
The incubation temperature of naturally (nest) incubated eggs is controlled by the hen. The recommended temperature within an artificial incubator depends upon the type of incubator being used. If the temperature exceeds by a degree or two degree Fahrenheit above the recommended temperature, it can kill chicks within a short period of time. Slightly lower temperatures will not kill the chick embryos, but can increase incubation times and produce weakened chicks. Temperature control of an incubator system using PID controller algorithm is implemented using Arduino board as a mini project. An electric bulb is used as a heating element, powered with 230 V supply. The power supply is controlled by a triac regulator to control the temperature. The PWM signal is used to control the ON-OFF speed of regulator, thereby controlling the power supplied to the bulb.
A number of machine operations such as welding, cutting, painting often have to be done on the parts of a product in an assembly line. The conveyor belt carrying the parts has to be stopped for these activities till the machine finishes its operation. An alternative is to move the machine with the product part for some time, during which the two are stationary with respect to each other. Thus, the operations can be done without stopping the conveyor belt. The machine is then brought back to follow the next part. This results in speeding up the assembly line. An FPGA based embedded control system is developed to achieve the interlocking by parallel processing the two motors avoiding the use of mechanical interlocks.

This project aims at position control of a high rpm and low torque DC motor using Arduino Uno (microcontroller development) board. The model for position control with the help of setup shown in Figure is obtained by approximating the velocity transfer function as FOPTD (First Order Plus Time Delay) model using step test and then deriving the position model by cascading an integrator. The models are obtained for both directions of motor (clockwise and counterclockwise). The identified models have parameter variations. Therefore QFT design technique is used to design a robust proportional controller to satisfy given stability, rise time and steady state error performance specifications. Position accuracy of ±1 degree has been achieved.
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