Rover Wheel Slip & Traction Simulator

Terrain

Slope angle 10°

Drive

Commanded wheel speed 12 cm/s

Telemetry

DRIVING

Slip ratio

Rover speed

0.0 cm/s

Traction force

0.0 N

Distance driven

0 cm

How it works

A driven wheel's motor spins its rim faster than the vehicle actually advances whenever the soil can't supply enough shear force to match it — the mismatch is the slip ratio:

s = (v_wheel - v_actual) / v_wheel
v_wheel = ω·r   (commanded rim speed)
v_actual        (rover's true ground speed)

Traction (drawbar pull) grows with slip but saturates — a real, well-documented terramechanics curve for wheel-soil interaction (the shape used to characterise the MER/MSL wheels' performance on granular soils):

μ(s) = μ_max·(1 − e^(−k·s))
F_traction = μ(s)·N,   N = m·g·cosθ
F_net = F_traction − m·g·sinθ − C_rr·N
a = F_net / m

On a slope, gravity's component along the surface (m·g·sinθ) and rolling resistance both fight the traction force. The simulation integrates this force balance every frame, so speed and slip settle to whatever equilibrium the soil and slope allow:

Hard regolith / basalt — high μ_max, traction saturates quickly at low slip: the rover drives normally.
Loose regolith — lower μ_max and slower saturation: noticeably more wheel spin for the same speed.
Sand trap — very low μ_max: past a modest slope the equilibrium slip approaches 100% and the wheels spin nearly in place — this is the physical mechanism that stranded NASA's Spirit rover in soft sand at Troy in 2009, ending its mobile mission.

Wheel angular speed always tracks the commanded value (the motor doesn't know it's slipping); only the rover's actual translation is limited by available traction.

Rover body + wheels Regolith / rock field

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