TECHNION - ISRAEL INSTITUTE OF TECHNOLOGY Department of Electrical Engineering Control and Robotics Lab Design a digitally controlled analog PID controller Designer: Idan Yahav Supervisor: David Gidony 1

PID controller - Intro 2 The PID controller helps get your output where you want it, with minimal overshoot, and with little error. PID stands for: P -Proportional, I - Integral, D - Derivative. We apply this functions on the error signal. V error is the difference between where you want to go (V set ), and where you're actually at (V sensor ). V error = V set - V sensor.

PID controller - Intro 3

Term Math Function Effect on Control System P Proportional KP x V error Typically the main drive in a control loop, KP reduces a large part of the overall error. I Integral KI x ∫ V error dt Reduces the final error in a system. Summing even a small error over time produces a drive signal large enough to move the system toward a smaller error. D Derivative KD x dV error / dt Counteracts the KP and KI terms when the output changes quickly. This helps reduce overshoot and ringing. It has no effect on final error. PID controller - Intro 4 The controller performs the PID mathematical functions on the error and applies their sum to a process

Goal Main goal : To design a digital controlled PID controller. Part A - Analog Design the analog amplifiers PID and summing. Part B – digital: Design a microcontroller that will control an LCD screen and a variable gain element. 5

Chosen Architecture 6 Amplifiers supply ±15[V]. Digital supplier 5 ]V[. Red arrows indicate digital potentiometer.

Part A : analog design Spec: Input signal is 0.1 [V] Functionality BW- 10m-200 [Hz] Issues Feedback amplifiers : stability check. R out and R in of the P and summing amplifiers. Check the synergy between the blocks. 7

P amplifier Rout=1 ohm PM is 87 Close loop: BW=19K. 8

D amplifier 9 Lowers the gain in high frequency and help stabilize the amplifier Main conflicts: Stability of the block. Functionality of the block

D amplifier 10 PM=87 Close loop BW = 200[Hz]

I amplifier 11 Cancel the affect of bias voltage Cancels affect of bias currents Main conflicts: Stability of the block. Functionality of the block

I amplifier 12 Cancel the affect of bias voltage Cancels affect of bias currents PM=20 Close loop BW 8m[Hz]

Summing amplifier Rin=Ri PM is 87 Close loop BW=17K. 13

Part B : Digital Design The microcontroller is like a small computer. It includes a CPU, memory and I/Os. In order to design the digital solution we need: C code (with a CCS compiler). Interrupts. (do not return to the start of main) Timers. Datasheets. 14

Part B : Digital Design For a single press: count = count ± 0.1 (depend on the button that was pressed). For a long press: count = count ± 0.9 the first time and count = count ± 1 on the rest. If count >10 :count=count-10.

Flow chart 16 Stop timer Start timer Count+0.1 In=1 Timer=0 In=1 Timer=1 In=0 Timer=x Start timer Count+1

Part B : Digital Design A function that writes to the screen was implemented 2 denounce solution were implemented 17

Opens and Next steps Stabilize the integrator. Design a power supply: ±15 [V], gnd, 5[V] and an adjustable voltage down to -5 [V]. Implement a code for the digital potentiometer. Design protection blocks for the card. Calibration solution. Design a printed card. Measurements on the card. 18

Q&A 19

References lating-resistor-and-capacitor-values-for-an-op-amp- differentiator-circuit-d _loop.htm lating-resistor-and-capacitor-values-for-an-op-amp- differentiator-circuit-d _loop.htm