Functionalised nonlinear structures employing structural instabilities for rapid response shape-shifting are emerging technologies with a wide range of potential applications. The truss is a widely employed model for such functionalised nonlinear structures; however, few studies have delved into its functionality when integrated with a complex dynamical system. This paper investigates its efficacy on enhancing the progression speed of a vibration-driven robot, known as the vibro-impact capsule robot, which is a piecewise-smooth dynamical system having abundant coexisting attractors. Bifurcation analysis of the capsule robot integrated with a truss is conducted for this purpose. Our numerical studies focus on the influence of the frequency and amplitude of the robot's driving force on its progression. Specifically, we compare the periodic responses of both the capsule robots with and without the truss, utilising the numerical continuation techniques for piecewise-smooth dynamical systems. Our studies confirm the advantage of using the truss when the driving force of the robot is significantly small. Additionally, we identify an optimal operational regime on the amplitude-frequency control plane, where the maximum robot speed is achieved for a given amount of power consumption. The numerical studies presented in this work provide a promising indication of the advantages offered by the truss for vibration-driven robots. This research underscores the significant potential of functionalised nonlinear structures to enhance the efficiency of small-scale robots operating under power limitations.
