1 8.1 Controller Parameterization for General Plants 2 8.2 H∞ PID Controllers for Unstable Plants 3 8.3 H2 PID Controllers for Unstable Plants 4 8.4 Performance Limitation and Robustness 5 8.5 Maclaurin PID Controllers for Unstable Plants 6 8.6 PID Design for the Best Achievable Performance 7 8.6 All Stabilizing PID Controllers for Unstable Plants