CRS F3, User Manual

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Chapter 5: Installation 47
99-05-31
Embedded Control and Power Electronics
One of the F3’s innovative features is the embedded servo control and power
electronics in the robot arm. This design reduces the computational load on
the controller, the volume and frequency of communications between the
robot and controller as well as the number of conductors in the umbilical
cable. In fact, the robot and controller communicate over a pair of optical
fibres. This improves the electrical noise immunity of the umbilical cable.
The embedded electronics consists of two amplifier modules, a servo gripper
I/O (SGIO) board, a double-actuation solenoid, a power conditioning module
(PCM) and a fibre board.
Amplifier modules
Each amplifier module controls three joints. The waist module which can be
found inside the shoulder casting provides servo control of and power to
joints 1, 2 and 3. In addition, it controls the brakes of these joints.
The wrist amplifier module provides the same functions for joints 4, 5 and 6
except these joints do not have brakes. It is located in the side of the wrist
without the air manifold.
Servo control in the F3 robot is based on the classical PID (proportional,
derivative and integral) scheme. Absolute encoders (defined earlier) provide
input to this DSP-based controller. Its outputs are current commands to the
PWM (pulse width modulation) amplifier stage which switches current in the
motors using Hall sensor feedback.
Warning! Make sure the wrist is kept away from liquids and collision. Entry of liquids
into the wrist may lead to shorts in the wrist amplifier module and other embedded
electronics. The plastic wrist cover also cannot adequately protect the electronics from
damage in case of collision. The waist amplifier module is in the shoulder casting, and is
better protected, but precautions are still necessary.
SGIO
The servo gripper input/output board consists of control electronics to
provide four (4) digital input channels and four (4) output channels in
addition to control of the servo gripper, if there is one (see below for more
information on end-of-arm I/O and servo gripper options). In the default
configuration, two of the digital output lines are used to switch a double
action servo valve.
Pneumatic Valve
A double-actuation pneumatic valve is provided in the default configuration
of the F3 system and maintains the state of an air-driven tool even after
controller power is shut down. This mechanism is controlled by the SGIO
board and supplied by an internal 3 mm air line. The outlets at the air
manifold are designed for 3 mm lines. The inlet at the base next to the
umbilical receptacle is designed for a 6 mm hose.
The pneumatic valve is the default end-effector. It is controlled by the first
two output channels of the SGIO interface. Therefore, do not try to command
these two I/O channels if the system is configured for a pneumatic tool.
PCM
The power conditioning module is located inside the shoulder casting. It
converts and distributes all power lines coming into the robot. It is also the
junction for the brake release lines for the lower three joints. In addition, it