FYP II Week 8 - 10: LabVIEW Programming

LabVIEW block diagram

LabVIEW Front Panel

This LabVIEW programming use PID controller, PID controller is a proportional–integral–derivative controller (PID controller) is a generic control loop feedback mechanism (controller) widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process control inputs.

Block diagram of PID controller

The PID controller calculation (algorithm) involves three separate constant parameters, and is accordingly sometimes called three-term control: the proportional, the integral and derivative values, denoted P, I, and D. Heuristically, these values can be interpreted in terms of time: P depends on the present error, I on the accumulation of past errors, and D is a prediction of future errors, based on current rate of change. The weighted sum of these three actions is used to adjust the process via a control element such as the position of a control valve, or the power supplied to a heating element.

Simulate signal block is use to convert analog signal into square wave signal. By using this it can control the rotation speed of motor especially servo motor because it need a pulse to determine an angle of rotation.

This is delay function it used to suspend execution of a program for a particular time. Several functions are available to help you control the timing or speed your program performs its actions.

A programmable logic device or PLD is an electronic component used to build reconfigurable digital circuits but in LabVIEW we can use it as a block. Unlike a logic gate, which has a fixed function, a PLD has an undefined function at the time of manufacture. Before the PLD can be used in a circuit it must be programmed, that is, reconfigured.

The picture below show what happening when the program is running:

when the sensor above set point

when the sensor under set point

Testing the program: