Chapter 4

Question 1

Twitch

Answer 1

• Error is at the highest at the start
• Kp commands a high voltage
• Wheels may not engage at the same time

solution:
- gradually increase power up to the point where you switch over and issue a command

Question 2

Backlash

Answer 2

• In gears there is a clearance between the gears where it can turn but it does not mesh with the conjugate pair. Over multiple gears these add up

Solution: Have an offset of about 5 degrees

Question 3

Slip

Answer 3

• This is when it is commanding too much torque and there is not enough friction
  -Driving forward but the distance it not measured

Solution: Raise the arm up to the maximum so it is closer to the centre of mass and providing more force on the back wheels.
Also slowly increase power.

Question 4

Integrator Windup
Why AND How does it happen?

Answer 4

-This is when the actuator is saturated
- Only for PI controllers
- The plants responds slower
- The plant demands more power but no more power can be given
- Area keeps increasing since error is not reached
-Controller cannot reverse action until area is small

Question 5

Integrator Wind Up
Why is that an issue?

Answer 5

• Significantly increases overshoot
• Longer time to settle and reach desired value
  -Prolongs actuator saturation - can damage actuator

Question 6

Integrator Wind up
Solution

Answer 6

• Reducer controller gains (slows the response of the system)
• When saturating don’t integrate
• Limit the integral

Question 7

Why does it start integrating earlier even if we see saturation?

Answer 7

It dips below saturate and as soon as it dips below, it starts integrating that brings it back up, that is why there is an error build up.

Question 8

Why do you not set the integral to zero

Answer 8

You negate the usefulness of the