In practical terms it automatically applies accurate process control bequette solution manual pdf responsive correction to a control function. The PID algorithm restores the actual speed to the desired speed in the optimum way, without delay or overshoot, by controlling the power output of the vehicle’s engine. The first theoretical analysis and practical application was in the field of automatic steering systems for ships, developed from the early 1920s onwards.
Today there is universal use of the PID concept in applications requiring accurate and optimised automatic control. PID controller in a feedback loop. The block diagram on the right shows the principles of how these terms are generated and applied. For example, if the error is large and positive, the control output will be proportionately large and positive, taking into account the gain factor “K”. Using proportional control alone in a process with compensation such as temperature control, will result in an error between the setpoint and the actual process value, because it requires an error to generate the proportional response. If there is no error, there is no corrective response. SP-PV error and integrates them over time to produce the I term.
For example, if there is a residual SP-PV error after the application of proportional control, the integral term seeks to eliminate the residual error by adding a control effect due to the historic cumulative value of the error. When the error is eliminated, the integral term will cease to grow. This will result in the proportional effect diminishing as the error decreases, but this is compensated for by the growing integral effect. SP-PV error, based on its current rate of change.