Hydraulic Actuation

 Joint motion was accomplished by hydraulic actuators controlled by servo valves. A

pressure compensated hydraulic power unit (Figure 4.14) provided hydraulic power to the

actuators. A 1 liter accumulator, charged to 7000 kPa, was added to help maintain constant

hydraulic pressure. Bird-Johnson SS-2-100 rotary actuators were utilized for actuating joints 0

and 1 (Figure 4.15). These actuators had splined shafts which interlaced with the splines that

were machined into the steel spindles that served as mounts for the outer and inner links.

Control of the fluid flow to these two actuators was achieved by Pegasus 3.8 liter-per-minute

(1.0 GPM), 120 series servo valves. The servo valves were connected to the actuators with

hydraulic manifolds which provided cross port pressure relief. Motion of the prismatic joint 2

was performed by a Hartmann HT-5 hydraulic motor (Figure 4.16) which was mounted to the

inner link of the robot. This motor was connected to the drive shaft of the pinion gear by a

Lovejoy coupling. It was controlled by a 18.9 liter-per-minute (5.0 GPM) Sundstrand MCV 103A



 Charged to 6900 kPa
 Lip Actuator
 Axis2
 Axis 1
 Axis 0

 Pressure Manifold
 Return Manifold Type 'T'
 Thermocouple

 0 |Axis2
 5 micronT Preset at Axis 1
 filter 17000 kPa A-- is 0

 o10 micron filter

 14000 kPa Weeage
 Weepage
 3.7 kW Motor drain lin.. To Hartmann
 1750 rpm -- case drain
 1750 rpm O SM -M---. I I case drain


Figure 4.14. Circuit diagram of hydraulic power unit.