ADAPTIVE CONTROL SYSTEM
Adaptive systems are the systems that are used when the plant parameters are changing with time. adaptive systems are combined with the techniques to make the system automatic controlled in real time.adapt means change the behavior to conform to new circumstances. the basic need of adaptive control system is to maintain the desired level of control plant parameters when the parameters of the plant or system is unknown (vary with time).
adaptive system is any physical system that is mostly designed from adaptive point of view. it is the composition of the algorithms developed for plant whose model contain unknown constant parameters.
adaptive controller is that which can modify the behavior of the plant processes when their are disturbances over the plant.
AN EXAMPLE OFADAPTIVE SYSTEM
consider a lumped parameter system of spring and damper shown in figure. We know that to study the response of the system it is required to study about the differential equation.
mx”+cx’+kx = 0 this is the differential equation of the system.
where m is the mass of the system
x is deflection of mass from it’s mean position
c is the viscous damping coefficient
k stiffness of spring
now there are two condition that are given below
if we consider that the parameter of dynamic model of the plant to be controlled are unknown but constant (here the constants are c & k). then we can generates the controller parameters if we know the value of constants (k&c).so in this case the adaptive control techniques provide an automatic tuning procedure in closed loop for the controller parameters. here we are assuming that the constants does not changes with environmental conditions. so after some time the effect of the adaption vanishes as the time is increases.
in this condition the parameters of the dynamic model of the plant to be controlled are unknown and also unpredictable. it means that the constant (k & c)have different value at different time.if we suppose that the environmental condition like temperature is change with time.then due to this the viscosity of the fluid (fluid in damper) also changes with respect to the temperature. in order to achieve the better acceptable performance parameters the adaptive control system has to be considered. in this case adaption is required at every instant. the requirement of the adaption does not vanishes as the time is increases. so this condition is also termed as continuous adaption.
Adaptive controllers are basically used to rectify the real time non-linearities. from the schematic we can easily understand that the control parameters are adjusted by an additional control system. this additional control system