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• ranaateeq

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• Fuerza
• Sistema de control
• Aceleración
• Ingeniería mecánica
• Dinámica (Mecánica)

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Name: Ateeq Ur Rehman

Registration no: SP14-REE-027/ISB

Cruise Control System (Progress report)

Contents

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Introduction Physical setup System equations System parameters State-space model Transfer function model

Introduction: Cruise control is the term used to describe a control system that regulates the speed of an automobile. The basic operation of a cruise controller is to sense the speed of the vehicle, compare this speed to a desired reference, and then accelerate or decelerate the car as required. The purpose of cruise control is to keep the velocity of a car constant. The driver drives the car at the desired speed, the cruise control system is activated by pushing a button and the system then keeps the speed constant. The major disturbance comes from changes of the slope of the road which generates forces on the car due to gravity. There are also disturbances due to air and rolling resistance. The cruise control system measures the difference between the desired and the actual velocity and generates a feedback signal which attempts to keep the error small in spite of changes in the slope of the road. Physical setup Automatic cruise control is an excellent example of a feedback control system found in many modern vehicles. The purpose of the cruise control system is to maintain a constant vehicle speed despite external disturbances, such as changes in wind or road grade. This is accomplished by measuring the vehicle speed, comparing it to the desired or reference speed, and automatically adjusting the throttle according to a control law.

Name: Ateeq Ur Rehman

Registration no: SP14-REE-027/ISB

We consider here a simple model of the vehicle dynamics, shown in the free-body diagram (FBD) above. The vehicle, of mass m, is acted on by a control force, u. The force u represents the force generated at the road/tire interface. For this simplified model we will assume that we can control this force directly and will neglect the dynamics of the powertrain, tires, etc., that go into generating the force. The resistive forces, bv, due to rolling resistance and wind drag, are assumed to vary linearly with the vehicle velocity, v, and act in the direction opposite the vehicle's motion. System equations Using Newton's law, the dynamic equation for this system is:

where u is the force from the engine. State-space model The state-space model of this equation now becomes:

Transfer function model Taking the Laplace transform of the governing differential equation and assuming zero initial conditions, we find the transfer function of the cruise control system to be: