Page 737 - Mechatronics with Experiments

PROGRAMMABLE MOTION CONTROL SYSTEMS 723
Step 2: Describe the operation of the machine in more detail.
1. Required modes of operation (setup mode, manual mode, auto mode, power-up
sequence things to do).
2. Required operator interface, that is what commands the operator will give,
what status information the operator will need, what data the operator can
change and monitor.
Step 3: Decide on the required hardware components and design integration of
the electromechanical system (mechanical assembly and electrical wiring of
components).
1. Actuators: servo motors, DC motors, hydraulic or pneumatic cylinders.
2. Sensors: encoder feedback, proximity switches, photo-electric switches.
3. Controllers needed: PLCs, servo controller, sensor controller.
4. Operator interface devices.
5. Motion transmission mechanisms: gears, lead-screws, timing belts.
Step 4: Develop application software
1. Top-down tree structure design of software.
2. Psuedo-code.
3. Code in specific programming language.
Step 5: Set up each programmable motion axis
1. Basic hardware check.
2. Power-up test.
3. Establish serial communication.
4. Servo tuning (K , K , K , K , K , … , values).
vf
af
p
v
i
5. Default parameter set-ups (default acceleration, deceleration, jog speed, max-
imum motion planning parameters).
6. Simple moves: Jog, Home, Single incremental motion (“Index”) parameters.
Step 6: Debug, test, verify performance.
Step 7: Documentation: document clearly so that later on someone else can debug and/or
modify the machine.

10.3 MOTION CONTROLLER HARDWARE AND SOFTWARE

The heart of a PMC system is the controller. The same controller can be used with dif-
ferent actuators such as electric servo, hydraulic servo, or pneumatic servo power. The
degree of intelligence and sophistication that can be designed into the system is largely
dependent upon the capabilities of the controller. The custom application software in the
controller uses the I/O hardware to define the logic between them and control the oper-
ation of the machine. The I/O hardware can be grouped into the following categories
(Figure 10.3):

1. Axis level I/O
(a) Servo control I/O:
Command signal to amplifier in the form of ±10 VDC range analog DC voltage

or PWM signal.
Feedback signal from the position sensor (encoder, resolver).

(b) Axis I/O:
Travel limits: positive and negative direction limits.

Home sensor input.

Amplifier fault input.