ElmoMC SimplIQ Software Manual - Manual (Page 226)

SimplIQ Software Manual The Controller
MAN-SIMSW (Ver. 1.4)
15-8
Only a subset of the controller parameters can be scheduled. The KG[N] parameters can
program sets of KP, KI gains, as well as one scheduled double-lead block at the high-order
filter. The other elements of the high-order filter cannot be gain scheduled.
The scheduling is automatic for GS[2]=64. GS[2]=0 selects the controller parameters of
KP[2], KI[2] and KP[3]. Other values of GS[2] directly select with of the available sets of
controller parameters is used.
Example:
If GS[2]=1, the proportional gain of the speed loop will be SpeedKpTable[1]. According to
Table 15-1 , SpeedKpTable[1] = KG[64].
15.4 Automatic Controller Gain Scheduling
The speed reference controls the controller gain scheduling. The goal of the algorithm is to
decrease the gains when the speed is low, because at low speeds, a large delay is added to
the encoder measurement, resulting in low bandwidth.
The gains are scheduled according to the reference speed. If the desired speed is high, the
encoder data is updated at a high rate so that the speed sensing delay is low. If the desired
speed is low, the encoder pulses are slow. For example, suppose that a speed of 200
counts/second is required. At this speed, there will be a new encoder count once per 5
milliseconds. The calculated speed will have an average 2.5-millisecond delay that may
adversely affect the stability of the control algorithm. For this reason, if the speed is low, the
controller bandwidth must be narrowed so that the extra sensing delay becomes tolerable.
The speed command is filtered so that the filtered value serves to fetch the relevant
controller scheduled parameters, KP, KI and some of the advanced filter parameters, from a
table. The filtering is required in order to avoid abrupt changes of controller parameters,
which can spoil the guaranteed stability of the gain-scheduled controller (assuming that
each selection set of speed controller parameters is a stable controller for its goal speed).
The speed range in which the scheduling is effective is approximately 0…10,000 counts/
second.