The role of the encoders in the R17 and as an R12 level 1 option is as watchdogs. The loop is closed after completion of each individual motion which is not the same as servo control. The R12 encoder option comprises miniature optical incremental encoders fitted to each axis.
Without encoders the R12 will run accurately and indefinitely open loop without error thanks to micro-stepping drives and accurate transmission. But if the robot suffers a collision then the controller does not know and carries on with the program even though the robot could be out of position. Such collisions usually only occur accidentally during programming and rarely during normal running. It is necessary to run the calibrate routine after such a collision.
If the encoder option is not fitted ST provides a software solution in the form of a quick calibration check that can be included in every robot cycle or n cycles. If there is an error it is reported and the system stops.
A specially calibrated level 2 option is also available whereby the encoders accurately read back the position of the robot when de-energized. The robot can be positioned by hand and its position updated on pressing a key on the keypad. The kinematics software then computes the exact X-Y-Z position of the robot with the hand pitch and roll in degrees.
|High power micro-stepped hybrid stepping motors,
optional encoder watchdogs
|500mm/20ins in any direction; 360 degree waist rotation
|0.1mm (see note)
|nominal 500g, max 1Kg (2.2lbs) at flange
(repeatability and speed degrade with increasing payload and reach).
droop at 250mm at nominal payload:
droop at max reach with max payload:
|Shoulder 180 deg/sec, Elbow 270deg/sec, Waist 180 deg/sec.
|Standard cycle time:
|Max torque for hand pitch or roll:
|2 Nm (repeatability figures degrade).
|Robot 12.8Kg/28lbs Controller 11kg/25lbs
|110/240v ac 420VA (standard controller)
|0 – 30C (wider range optional)
|Class 2 stop circuit, stall detect, risk assessment guide.
Optional high intensity red LEDs along the arm serve as awareness barrier.
|Approx 40-50dB at 1m.