TERRAMECHANICS BASED MODEL FOR PATH TRACKING OF A SIX WHEEL ROCKER BOGIE ROVER
ABSTRACT
Planetary rovers are gaining importance in the field of exploration which may be autonomous or semi-autonomous. Such rovers need to traverse large distance over the terrain and perform geological experiments. The path planning generates a safe path for rover to reach its destination. It is important to compute the various parameters of the rover needed to maintain a constant linear velocity so that the errors in tracking the generated path can be minimised. This paper includes the use of terramechanics of the lunar regolith to predict the mobility of the rover for path tracking purpose. Path tracking ensures that the rover reaches its destination by following the path it was intended to move on. A kinematic model of a six wheel rocker- bogie…show more content… Rocker-Bogie 3D model.
Path tracking
The digital elevation map (DEM) gives us knowledge of the terrain. This is provided by the navigation camera and the path planning generates the optimum path that the rover must travel which has the least energy consumption. To trace the path, wheel-soil interaction parameters must be taken into account and its effects are explained in the figure 2.
Figure-2. Rover path tracking
The above figure signifies the effect of terramechanics on the rover capability to track a path. Path 1 is the path traced by the rover ignoring the effects of terramechanics and path 2 is the path traced by the rover considering terramechanics. If the rover was to move on a rigid surface, the wheels would not slip maintaining a constant linear velocity ?v? for a constant angular velocity of ??? as per the equation: v=r?, where r is the radius of the wheel (1)
But since the terrain surface is covered by loose soil, the wheels will be subjected to a slip value of ?i? thus altering the linear velocity as per equation (2)