Robotics 1

On-Off vs Linear Control

On-Off vs Linear Control

In this video, we learn about the trade-off between speed, stability, and accuracy in a control algorithm. We use our on-off control code for the PSoC from last time, and adjust the speed-accuracy-stability trade-off to achieve stable motion.

In this video, we learn about the simplest type of linear control: proportional control. We learn the difference between on-off control and proportional control, both of which are types of feedback control. We write some code for the PSoC to control the position of the rack and pinion using proportional control, then we find a good proportional gain value by testing different values and observing the results.

To complete this lab activity, make a video that includes the following in one video:

Undergrads only:

(1) You saying your name

(2) Your rack and pinion moving back and forth between two points using proportional control for two different values of Kp

(3) You commenting on the effects on stability, accuracy, and speed that you observe between the two values of Kp you are showing for point 2

Grads only:

(1) You saying your name

(2) A step response you captured from your rack and pinion using proportional control, while critically damped

(3) State what Kp value gave a critically-damped response

(4) Calculations for the rise time, peak time, settling time, overshoot, and steady-state error for one step response you captured from your rack and pinion

Undergrads only:

(1) You saying your name

(2) Your rack and pinion moving back and forth between two points using proportional control for two different values of Kp

(3) You commenting on the effects on stability, accuracy, and speed that you observe between the two values of Kp you are showing for point 2

Grads only:

(1) You saying your name

(2) A step response you captured from your rack and pinion using proportional control, while critically damped

(3) State what Kp value gave a critically-damped response

(4) Calculations for the rise time, peak time, settling time, overshoot, and steady-state error for one step response you captured from your rack and pinion

Note: Graduate students did these 'blue' videos last time. They can skip the blue videos this time.

In order to become more sophisticated with our motion control, we need a way to quantify the 'goodness' of our control algorithms and gain values. To do this, we need to be able to examine values collected by the PSoC more closely. In this video, we learn how to set up UART communication between the PSoC and the computer, so that we can use the computer to more closely examine values collected by the PSoC.

In this video, we learn how to send values from the PSoC to the computer. We learn how to use Python to save those values first in an array, then in a text file. Finally, we plot the values in Excel to see the motion of the rack and pinion with our Proportional control from last time.

In this video, we learn how to find some quantifiable measures of speed, stability, and accuracy from the time response of the rack and pinion. We measure rise time, peak time, settling time, overshoot, and steady-state error. We make these measurements for three values of Kp in our proportional control, and we note the trends in these values for increasing or decreasing values of Kp.

In this video, we find the proportional gain that gives a 'critically damped' response of the rack and pinion. We do this experimentally by trying a gain, calculating the characteristics of the step response, then increasing or decreasing the gain appropriately.