Modeling, Analysis, and Control of an Actively Reconfigurable Planetary Rover for Traversing Slopes Covered with Loose Soil

Abstract

Future planetary rovers are expected to probe across steep sandy slopes such as crater rims where wheel slippage can be a critical problem. One possible solution is to equip locomotion mechanisms with redundant actuators so that the rovers are able to actively reconfigure themselves to adapt to the target terrain. This study modeled a reconfigurable rover to analyze the effects of posture change on rover slippage over sandy slopes. The study also investigated control strategies for a reconfigurable rover to reduce slippage. The proposed mechanical model consists of two models: a complete rover model representing the relationship between the attitude of the rover and the forces acting on each wheel, and a wheel‐soil contact force model expressed as a function of slip parameters. By combining these two models, the proposed joint model relates the configuration of the rover to its slippage. The reliability of the proposed model is discussed based on a comparison of slope‐traversing experiments and numerical simulations. The results of the simulations show trends similar to those of the experiments and thus the validity of the proposed model. Following the results, a configuration control strategy for a reconfigurable rover was introduced accompanied by orientation control. These controls were implemented on a four‐wheeled rover, and their effectiveness was tested on a natural sand dune. The results of the field experiments show the usefulness of the proposed control strategies.

Slippage and immobilization detection for planetary exploration rovers via machine learning and proprioceptive sensing

“…In contrast, this paper focuses on features directly measured by sensors onboard the rover. Finally, it is worth to note that this paper tackles the slippage problem from an algorithmic (software) viewpoint more than from a mechanical solution …”

“…Finally, it is worth to note that this paper tackles the slippage problem from an algorithmic (software) viewpoint more than from a mechanical solution. [33][34][35]…”

Lateral Stability of a Mobile Robot Utilizing an Active Adjustable Suspension

“…A stability pyramid method is used to evaluate the robot's stability. We make several assumptions to simplify the problem [22]:…”

“…Chen and Genta developed a dynamic model for wheeled planetary rovers with active suspensions; when the attitude of the rover is controlled, strong lateral wheel slips are prevented [21]. Inotsume et al proposed a reconfigurable rover and modeled the relationship between the attitude of a rover and its slip, showing that a rover could traverse slopes covered with loose soil with less downhill slippage by properly adjusting its configuration [22,23]. Gao et al developed a hillside vehicle power chassis with a balanced rocker suspension mechanism.…”

Slide-Down Prevention for Wheeled Mobile Robots on Slopes

“…Sliding down can alter the vehicle's maneuvering ability (Singh & Krishna, 2016) or get the robot stuck (Yamauchi et al, 2014). However, this relevant problem has received less attention than traction wheel slippage (Balakrishna & Ghosal, 1995) (Thueer & Siegwart, 2010), tip-over prevention (Morales et al, 2013), or vehicle sideslip (Cariou, et al, 2009) (Inotsume et al, 2013). This paper proposes slide-down prevention for wheeled robots by real-time computation of a straightforward stability margin for a given ground-wheel friction coefficient.…”