Technical information

The AHMCT Research Center, in conjunction with the Caltrans Equipment Service Center, has rebuilt the

Debris Removal Vehicle (DRV). The following was the scope of the project and plan of action as

determined by both of the above groups.

Project Scope

• Evaluate the existing mechanical, hydraulic, and electronic control structure.

• Devise a plan of action to repair the existing project with the goal of re-

deployment for the purposes of field operational testing and evaluation.

Plan of Action

• Install and implement a hydraulic and electronic control system that exhibits

reliable and controllable motion.

• Make reasonable structural repairs to the azimuth joint and short arm sections.

Due to the nature of a rebuild as opposed to a redesign, several design considerations

were made. Reasonable changes and repairs were implemented to limit the time

involved. During the rebuild process there were several concerns that arose. The

following are the known concerns and a portion of the design considerations of the

project.

Design Considerations

• Due to the need for control versatility and reliability a new controller was

chosen. The ZWorld controller was a cost effective solution. The existing

PWM Amplifiers were tested and found to be sufficient for the parameters of

this project. The existing potentiometers used for analog position feedback

were not reliable or of the quality needed for this application. Therefore,

industrial grade potentiometers were chosen to replace the existing

components. The analog feedback is sufficient for the required accuracy of

the system. The 3 axis, 4 pushbutton, 1 trigger, joysticks are industrial grade

and commonly found in commercially available equipment. The joysticks are

reliable and provide adequate versatility.

• The existing arm exhibited ratcheting motion when the hydraulics were in an

over-running condition. Sun counterbalance valves, designed for use with

over-running hydraulic circuits, were installed to eliminate the ratcheting.

Utilizing the counterbalance valves reduces the stresses in the arm by

eliminating the excessive accelerations encountered during ratcheting, and

furthermore, allows for velocity control. Overpressure relief valves were

installed to protect the structure of the arm. The hydraulic spool valves on the

dump body were leaking and causing creep. A main flow poppet valve was

installed to eliminate the creeping problem. The dual hydraulic reservoir