Design and control of an enclosed dual-screw robot chassis for soft-terrain locomotion

Abstract Mobile robots operating on soft, low-bearing terrain often suffer from sinkage, slip, steering difficulties, and particle intrusion into exposed transmission components. This study proposes an enclosed dual-screw robot chassis for soft-terrain locomotion. The chassis employs two independently driven screw wheels with built-in motors and sealed transmission components. A simplified propulsion-force analysis and a kinematic model were developed to describe the forward, backward, rotational, and differential-steering motions of the chassis. On this basis, a finite state machine (FSM)-based control strategy was designed to coordinate the two screw wheels, enable smooth transitions between motion modes, and provide a soft-stop function. A physical prototype was evaluated in loose sand in terms of speed regulation, travel speed, slip ratio, sinkage, and sealing performance. The screw-wheel rotational speed showed a strong linear relationship with the chassis travel speed, with a coefficient of determination of 0.9974. Within the tested speed range, the maximum slip ratio was approximately 3.6%, and the maximum sinkage was approximately 79 mm. After 30 min of continuous operation, no obvious sand intrusion was observed inside the enclosed screw-wheel cavity. These results provide preliminary evidence for the feasibility of the proposed chassis for soft-terrain locomotion, while further validation under broader terrain conditions is still required.