Anti-slip power-assist for electric carts via switched force and slip-acceleration control for responsive assistive motion

Responsiveness is an important requirement in power-assist systems because it directly affects the operator's ability to maneuver the vehicle safely and intuitively. However, in wheeled systems such as electric power-assist carts, responsiveness can be severely degraded on low-friction surfaces due to wheel slip and the nonlinear tire-road friction characteristic. Most existing power-assist control methods for electric carts either neglect operation under low-friction conditions or rely on high-latency body velocity measurements for slip suppression, which can reduce responsiveness. This paper proposes an anti-slip power-assist control strategy based on a switched force and slip-acceleration control scheme governed by a predefined slip-velocity threshold. The slip-acceleration controller is based on wheel acceleration control and uses cart body acceleration feedback to indirectly regulate slip velocity. Low-latency motor encoder and cart acceleration measurements are employed in the continuous feedback loop, while slip velocity information is used only for switching decisions. Simulation and experimental results demonstrate stable and responsive power assistance. Compared with conventional power-assist control, the proposed method approximately halves the response delay and reduces the root-mean-square slip velocity by about three times, resulting in improved assistive motion performance under slippery conditions.