Design and Analysis of New Haptic Joysticks for Enhancing Operational Skills in Excavator Control

The design perspective of interfaces has strong implications on operator intuition and safety. Haptics enabled user interfaces can enhance operator skills and enhance interactivity. In this paper, an innovative method of haptic feedback in joysticks is presented for excavator control. Haptic illusion in the device is generated with the concept of the variable stiffness actuation mechanism. The force feedback (FFB) is rendered through “haptic links,” based on the effect of digging force at each joint. The stiffness in the device varies dynamically with the load and restricts the operator motion with a resistive torque in the range of 0–0.9 Nm. The haptic joystick aims to render high-fidelity kinesthetic feedback that can help to mitigate the operator error in loading operations. The user evaluation with the joystick showed an improvement of 40% in the volume of material removed and a significant drop in error rate related to force patterns and collisions.

Modeling, Identification, and Control of a Discrete Variable Stiffness Actuator (DVSA)

A branch of robotics, variable impedance actuation, along with one of its subfields variable stiffness actuation (VSA) targets the realization of complaint robotic manipulators. In this paper, we present the modeling, identification, and control of a discrete variable stiffness actuator (DVSA), which will be developed for complaint manipulators in the future. The working principle of the actuator depends on the involvement of series and parallel springs. We firstly report the conceptual design of a stiffness varying mechanism, and later the details of the dynamic model, system identification, and control techniques are presented. The dynamic parameters of the system are identified by using the logarithmic decrement algorithm, while the control schemes are based on linear quadratic control (LQR) and computed torque control (CTC), respectively. The numerical simulations are performed for the evaluation of each method, and results showed the good potentialities for the system. Future work includes the implementation of the presented approach on the hardware.

Mechanical Simplification of Variable-Stiffness Actuators Using Dielectric Elastomer Transducers

Legged and gait-assistance robots can walk more efficiently if their actuators are compliant. The adjustable compliance of variable-stiffness actuators (VSAs) can enhance this benefit. However, this functionality requires additional mechanical components making VSAs impractical for some uses due to increased weight, volume, and cost. VSAs would be more practical if they could modulate the stiffness of their springs without additional components, which usually include moving parts and an additional motor. Therefore, we designed a VSA that uses dielectric elastomer transducers (DETs) for springs. It does not need mechanical stiffness-adjusting components because DETs soften due to electrostatic forces. This paper presents details and performance of our design. Our DET VSA demonstrated independent modulation of its equilibrium position and stiffness. Our design approach could make it practical to obtain the benefits of variable-stiffness actuation with less weight, volume, and cost than normally accompanies them, once weaknesses of DET technology are addressed.