Digital PID controller

The performance of the interacting controller is almost as good as the noninterac ting controller on most processes, but the tuning rules differ because of the above relationships. With digital PID controllers, the noninteracting version is commonly used. 

Digital PID controller. From equation (4.92), a continuous PID controller can be written as... 

Inserting this value of. v into the denominator of equation (7.98), still yields a digital PID controller of the form shown in equation (7.100) where... 

Proportional plus integral plus derivative (PID) feedback controllers, 20 692-693. See also Digital PID controllers Proportioning, 26 226 batch, 26 249-251... 

The digital PID controller is implemented as a recursive filter with a biquadratic transfer function. Controller wordlength, set-point input, controller output, and controller parameters are 10-bit fixed-point values in the range [0,1). The controller parameters also have an additional sign-bit. 

A 16-bit programmable frequency divider, which facihtates the selection and scaling of the controller gains, provides the sampHng clock of the digital PID controller. The frequency divider has an input clock of 1 MHz. 

Example 27.5 Discrete-Time Model of a Digital PID Controller... 

Consequently, the control action of a digital PID controller is determined by the following discrete-time model ... 

Gas chromatograph feedback controller, which uses the velocity algorithm for digital PID control, discussed in Section 12.4.3.4 to calculate flow correction factors for the monomers from the gas chromatograph measurement of the actual monomer feed composition. This controller provides the necessary integral action so that the offset between the actual reactor monomer feed composition and its set point, which may be caused by flowmeter inaccuracies or other unmeasured disturbances, is niinimized. 

There are two alternative forms of the digital PID control equation, the position form and the velocity form, A straightforward way of deriving a digital version of the parallel form of the PID controller (Eq. 8-13) is to replace the integral and derivative terms by finite difference approximations. 

In this section, the main emphasis is on the digital PID controller and how it should be tuned. Digital versions of the PID controller in the form of difference equations were previously presented in Eqs. 8-26 and 8-28... 

During the second semester of the sequence, the robot parts were either fabricated in-house, or purchased, and the structure was assembled. The EE s developed their system-level design into circuit and software details, and then built and programmed the control system. They completely built a bus based multi-processor system, with one Intel 8085 microprocessor for digital PID control on each of the three cartesian axes, one 8085 to handle the gripper and sensor inputs, and one 8085 to coordinate communications on the bus and to a host personal computer. They also designed and built sensor interfaces and pulse-width-modulated power amplifiers for the dc motor actuators. 

---