Instrumentation

The robot arm is fully instrumented to provide full state feedback for the entire system. The pump, tank and cylinder pressures are fitted with dynamic pressure sensors to provide pressure information at any point in the hydraulic system. The pump, tank and cylinders driven by the proportional directional valve and the servo valve make use of Entran EPXH-X01-2.5KP pressure transducers with an external amplifier. The Entran pressure transducers are responsive to pressure changes up to 300 KHz. The programmable valve makes use of two Omega PX603 pressure transducers with internal amplifiers. The Omega pressure transducers have a response time of 1 ms. The pressure sensors have a sensing resolution of 1.035x10^{5} Pa.

The robot arm is equipped with joint encoder at all three joints to provide the position feedback information. The encoders are BEI HS35 Incremental Optical Encoders with a sensing resolution of 4096 counts per turn or approximately 0.09 deg. In addition, all three hydraulic cylinders have built-in Tempsonic LDT sensors, which provide the position and velocity information of the cylinder movement. With an RS422 Digital Personality Module plus quadrature signal decoder, the LDT sensor provides a cylinder position sensing resolution of 0.001 inch. With an Analog Personality Module, due to the noise that corrupts the analog sensing output signal and the resolution of the ADC of the data acquisition system, the effective cylinder sensing resolution is around 0.5 mm. Currently, the lab has one digital module and three analog modules.

Clear here to see the locations of the LDT position sensors and the optical encoders.

In addition, a stand alone Omega FTB-102 turbine flowmeter calibrated at 40 C for Texaco Rando HD hydraulic fluid with a viscosity of 94 centistrokes at 40 C is used to obtain the valve mapping of various valves. The flowmeter incorporates an Omega FLSC-35B Signal Conditioner, and is mounted on a movable stand providing the correct pipe lengths for flow straightening and incorporates a check valve to protect the flowmeter and a manually adjustable needle valve to enable pressure drop adjustments, as shown here.