Allenair double acting
 hydraulic cylinder
 2.22 cm bore
 5.08 cm stroke







 3-way solenoid valve



 STo Return
 SManifold


 Pressure reducing
 valve set to 3400 kPa

 L ---J



 From Pressure
 Manifold

Figure 4.17. Circuit diagram of picking mechanism lip actuator.


chosen for their high precision and linearity. In both cases, the potentiometer body was

mounted to a plate which was attached to the actuator. The shaft of the potentiometer was

connected directly to the back side of the moving shaft of the actuator. A voltage was applied

across each of the potentiometers. The voltage across the wiper of the potentiometer was

proportional to the angular position of the rotary actuator and thus the position of the axis.

This voltage drop was quantified by a 12-bit, 5 volts analog-to-digital (A/D) converter.

 On joint 0, the potentiometer was required to relate a total motion of approximately 78

degrees to a voltage ranging between -5 volts and +5 volts. The potentiometer was supplied

with +5 volts to the positive side and -12 volts to the negative side creating a voltage

difference of 17 volts across the 360 degrees of the single turn potentiometer. The result was a

resolution of approximately 19 bits per degree of rotation of the potentiometer wiper shaft

(0.0520/bit). A summary of the range of motion for joint 0 and the A/D bits read for some critical

positions is presented in Figure 4.19.