SUMMARY

Supplying haptic or force feedback to operators using hydraulic machinery such as excavators has the potential to increase operator capabilities. Haptic robotic human-machine interfaces enable several enhancing features including: coordinated motion control and programmable haptic feedback. Coordinated or resolved motion control supplies a more intuitive means of specifying the equipment's motion. Haptic feedback can be used to relay meaningful information back to the user in the form of force signals. These haptic forces can relay information about digging force acting on the bucket, programmable virtual constraints and system limitations imposed by the mechanism, maximum pressure or maximum flow. Incorporating this technology adds to the cost of the product by increasing the number of sensors, the required computing power and the complexity of the human-machine interface. In order to make this technology economically viable, the benefits must offset the additional cost associated with implementation. One way to minimize this cost is to not use high-end hydraulic components. For smaller backhoes and mini-excavators this means that the hydraulic systems are comprised of a constant displacement pump and proportional direction control valves. Characteristics that limit the performance of the system include: valve spool bandwidth, valve dead-band, delay and noisy force estimation from pressure sensors. Stability is also an issue. Modeling and control of the real test-bed was used to develop a virtual backhoe for human-in-the-loop testing. Using a virtual model for human testing is desirable from a safety point of view and allows for key parameters to be varied instantaneously. This tool will be used to measure the enhancement in operator control. Use of this virtual excavator was designed to enhance testing on the real machinery rather than replace it. Not only was the virtual simulator be modeled after test-bed, but the control algorithm used in the simulator was also the one used on the actual backhoe test-bed. The end goal of this project is to incorporate haptic control algorithms that work on low-cost systems and maximize the enhancement of operator capabilities.