pole balancing

Page numbers are for draft copy at present; they will be replaced with correct numbers when final book is formatted. Chapter numbers are correct and will not change now.

A simple control task is to move a trolly back and forth while balancing a pole on top. This is not practically useful, but helps test different control strategies. In particular, it has been used as a test case for reinforcement learning.

Used on Chap. 5: page 103; Chap. 16: pages 376, 379