Cruise Control 3 RETURN OF THE SPEED CONTROL JEFF FERGUSON, TOM LEICK

Overview Background Proposed Controller Expected Results Questions

Background Closed-loop speed control Maintain constant speed under varying loads Cruise control system in vehicles Improve on results from Labs 4 and 5

Open Loop Behavior Lab 4 experiments provided data for determining: Minimum speed control voltage input Speed to input voltage ratio Effects on speed by application of brake load as shown on the following slide

Closed Loop Behavior Lab 5 experiments provided data for determining: Simple proportional gain closed loop speed control system characteristics Tachometer scale factor (K T ) Effect of pre-amp gain on error voltage as Brake position increased

Proposed Controller Use PID Controller module Maintain speed (voltage at tach) for brake position 10 to within 5% of speed at brake position 0 More concerned with steady-state error than quickness of the response Little-to-no percent overshoot

Simulink Block Diagrams

Choosing Controller Parameters In ideal models, any incorporation of an integrator resulted in zero steady-state error Large integrators are difficult to realize 0.1 < K I < 0.5 K D = 0 Solve for K P using the PID tuning window to match desired response

PID Block Tuning Window from Simulink

Choosing Controller Parameters K P = 0.1 K I = 0.4 K D = 0

Zero Brake Response

PID Block Tuning Window from Simulink

Full Brake Response

Conclusion System is modelled after automotive speed control system Not a “fast” system to avoid abrupt accelerator changes Little/no overshoot to avoid seasick passengers Little steady state error for accurate system Expected challenge in adjusting the controller to obtain predicted response K I being bigger than K P and K D might cause problems Possible saturation from current limitations

Questions