PID = P + I + D
err = setpoint-processValue
P = K(err)
reset = reset + k/tau_i*err
I = reset //once err changes direction or zero reset =0
D = K/tau_i*(error-lastError); lastErr = err;
K : gain : this is twicked
K/tau_i : can also be twicled for optimal performance
tau_i : second per repeat k/tau_i*sum
or
repeats per minute : k*tau_i*sum
systems can use : P / PI/ I / PID / PD