Introduction - Control Techniques UD70 User Manual

8.2

Introduction

An advanced position controller and profile generator is built into the
operating system of the UD70. The function blocks are designed to provide
position control and profile generation from one of the following:
• position reference.
• speed reference.
• incremental cam table.
• digital lock (provided an auxiliary encoder is used).
The main features of the position control software are:
• slave position control using linear or S-ramps for the velocity profile.
• slave speed control using linear or S-ramps for the velocity profile.
• smooth switching between position and speed control.
• rigid or non-rigid digital lock with a slave ratio range of 8, accurate
to 8 decimal places.
• incremental cam table providing automatic control of the slave
position, relative to the master position.
• smooth switching from cam or digital lock control to position or
speed control
• position loop feedback source selectable between feedback (main)
and auxiliary (reference) encoder inputs.
• three term PID control loop (D term configurable as feed-forward or
derivative term) with the output written automatically to the fast
access speed reference (#91.02).
When using the position control loop, it is important that the drive is also
configured correctly. The drive must use #1.21 as the source of the speed
reference (#1.14 = 3, #1.15 = 1) and bipolar reference must be enabled (#1.10 =
1). The speed ramps should be disabled (#2.02 = 0) as the profile generation
blocks will provide ramp generation. To achieve optimum performance, the
speed loop gains within the Unidrive (#3.10, #3.11, #3.12) must be tuned
correctly, otherwise some instability may result.
The Unidrive will require a brake resistor if the drive is to achieve fast rates
of deceleration. The ramp mode on the Unidrive (#2.04) should be set to
fast ramps instead of standard controlled ramps.
Selection between the different blocks is controlled using individual bits
within registers _Q20% and _Q32%. These bits can be individually
addressed or accessed as a whole word.
e.g.
_ Q20% = 2
_ Q20%.1 = 1
8-2 Features
; set bit 1 of _ Q20% to 1, all other bits to 0
; set bit 1 of _ Q20% to 1, all other bits are unaffected
UD70
Issue code: 70nu2