tailieunhanh - 3 Parameter Setting of Analog Speed Controllers

Practical speed controlled systems comprise delays in the feedback path. Their torque actuators, with intrinsic dynamics, provide the driving torque lagging with respect to the desired torque. Such delays have to be taken into account when designing the structure of the speed controller and setting the control parameters. | 3 Parameter Setting of Analog Speed Controllers Practical speed controlled systems comprise delays in the feedback path. Their torque actuators with intrinsic dynamics provide the driving torque lagging with respect to the desired torque. Such delays have to be taken into account when designing the structure of the speed controller and setting the control parameters. In this chapter an insight is given into traditional DC-drives with analog speed controllers along with practical gain-tuning procedures used in industry such as the double ratios and symmetrical optimum. In the previous chapter the speed controller basics were explained with reference to the system given in Fig. assuming an idealized torque actuator WA s 1 . In this chapter the structure of the speed controller and the parameter settings are discussed for the realistic speed-control systems including practical torque actuators with their internal dynamics WA s . Traditional DC drives with analog controllers are taken as the design example. Delays in torque actuation are derived for the voltage-fed DC drives and for drives comprising the minor loop that controls the armature current. Parameter-setting procedures commonly used in tuning analog speed controllers are reviewed and discussed including double ratios symmetrical optimum and absolute value optimum. The limited bandwidth and performance limits are attributed to the intrinsic limits of analog implementation. Delays in torque actuation The driving torque Tem provided by a DC motor is proportional to the armature current ia and to the excitation flux Pp. The torque is found as Tem km pia where the coefficient km is determined by the number of rotor conductors Nr km Nr 2 n . The excitation flux is either constant or slowly varying. Therefore the desired driving torque T is obtained by injecting the current ia Tief km P into the armature winding. Hence the torque response is directly determined by the bandwidth achieved in controlling the .