Terramechanics-Based Mobility Failure Compensation and Soil Manipulation (I)

Abstract

In this paper, we enable new mobility and manipulation modes for wheeled planetary exploration rovers through the use of terramechanics modeling and field experiments. Useful modes of wheel-based soil manipulation and examples of rovers driving with degraded mobility systems are first demonstrated in lunar and Martian analog environments. We show a full-scale rover use its wheels to dig trenches up to 10.6 cm deep, dig holes to estimate soil characteristics, and modify terrain to make it accessible to a smaller robot. We also measure the impact of actuator failure on a rover in lunar simulant. Here, we show the slip doubled on moderate slopes for a damaged drive motor, which would exceed the rover's operational limits for slip, motivating the need for driving strategies that mitigate mobility loss. We then develop an optimization framework which uses a recently developed terramechanics model to automatically generate both open and closed-loop driving strategies for planetary rovers performing terrain manipulation or operating in a degraded state with no need for hand tuning of behaviors. Finally, we demonstrate the generated driving strategies for soil manipulation and mobility compensation on a rover in a controlled lab setting, where we show that 1) mobility is maintained while manipulating soil; and 2) mobility is regained while experiencing failure of steer and drive actuators.