haptic control of hydraulic machinery using proportional valves

Some of the first researchers to propose the application of force feedback to hydraulic
systems such as excavators were Starzewski and Skibniewski [107]. They predicted
enhancements due to coordinated motion and “feel” or haptic feedback that
could be provided by such an interface. This concept paper predicted the commercial
use of such systems when it was technically and economically feasible. Patents related
to haptic or force feedback devices to control hydraulic machines were received
by Caterpillar Inc. [16] in the same year that his paper was published and by Kraft
[75] two years later. Like many other robotic researchers with an interest in excavators,
Skibniewski turned toward autonomous robotic excavators that could work
independently of humans instead of with humans [38, 63, 84, 126, 134, 139]. Others
in academia [9, 76, 121, 133] and the nuclear industry [8, 7, 15, 78, 59] have focused on
coordinated teleoperation of excavators with various levels of haptic feedback. By the
early 1990s, this topic was explored by the nuclear industry: HAZ-TRAK remotely
operated excavator [8, 78] and a telerobotic small emplacement excavator [15]. Better
documented work was conducted at the University of British Columbia on resolved
mode teleoperation by Sepehri et al. [121] and force feedback of hydraulic machines
by Parker et al. [109]. An impedance based teleoperation scheme designed for transparency
was later implemented on a mini-excavator and presented by Salcudean et
al. [120] and Tafazoli et al. [133]. Krishnaswamy and Li used a passive control based
on bond graphs to control a backhoe. One advantage of the passivity approach that
it is inherently safe.
Coordinated control is a subtle, but a profound improvement over conventional
hand controllers that work in joint space. Using joysticks that individually control the
joints of the manipulator puts a “high perceptual and psychomotor demand” on the
operator [141, 142]. Using coordinated motion control and a single hand controller
whose motion corresponds directly to the slave manipulator reduces this mental load
by doing the inverse kinematics for the operator. Human-in-the-loop experiments
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