Design and field testing of a rover with an actively articulated suspension system in a Mars analog terrain

Abstract

This study presents the electromechanical design, the control approach, and the results of a field test campaign with the hybrid wheeled‐leg rover SherpaTT. The rover ranges in the 150 kg class and features an actively articulated suspension system comprising four legs with actively driven and steered wheels at each leg’s end. Five active degrees of freedom are present in each of the legs, resulting in 20 active degrees of freedom for the complete locomotion system. The control approach is based on force measurements at each wheel mounting point and roll–pitch measurements of the rover’s main body, allowing active adaption to sloping terrain, active shifting of the center of gravity within the rover’s support polygon, active roll–pitch influencing, and body‐ground clearance control. Exteroceptive sensors such as camera or laser range finder are not required for ground adaption. A purely reactive approach is used, rendering a planning algorithm for stability control or force distribution unnecessary and thus simplifying the control efforts. The control approach was tested within a 4‐week field deployment in the desert of Utah. The results presented in this paper substantiate the feasibility of the chosen approach: The main power requirement for locomotion is from the drive system, active adaption only plays a minor role in power consumption. Active force distribution between the wheels is successful in different footprints and terrain types and is not influenced by controlling the body’s roll–pitch angle in parallel to the force control. Slope‐climbing capabilities of the system were successfully tested in slopes of up to 28° inclination, covered with loose soil and duricrust. The main contribution of this study is the experimental validation of the actively articulated suspension of SherpaTT in conjunction with a reactive control approach. Consequently, hardware and software design as well as experimentation are part of this study.

Common Data Fusion Framework: An open-source Common Data Fusion Framework for space robotics

“…(2) Experiments performed in Morocco with Sher-paTT: We performed several experiments with the SherpaTT robot, 43 the HCRU as an additional sensor module, and a differential GPS (D-GPS) module for ground truth pose estimation (see Figure 7). Ground truth digital elevation maps with 4 cm resolution are available for the test site.…”

Efecto de la Suspensión en el Seguimiento de Trayectorias en Robots Moviéndose Sobre Terrenos duros con Diferente Rugosidad

“…Por este motivo, muchos investigadores han trabajado en el desarrollo de nuevos robots, generando alternativas que incluyen: robots con orugas [11] y múltiples cuerpos [12], robots con patas [13], robots híbridos construidos con varios sistemas de locomoción (por ejemplo: patas y ruedas) [14], robots con mecanismos (como el Rocker-bogie [15]) que le permite amoldarse al terreno sin la adición de actuadores y robots con diferentes sistemas de suspensión [16]. Al respecto, es posible encontrar robots con suspensión pasiva [17], donde los sistemas que la conforman (resorte-amortiguador) no reciben energía desde el exterior.…”

Efecto de la suspensión en la estabilidad al vuelco y direccionamiento de robots moviéndose sobre discontinuidades de terreno

“…Suspensión activa si se adicionan actuadores que permitan introducir o disipar energía del sistema (Reid et al, 2016); y por último, semiactiva si el coeficiente de amortiguamiento en los amortiguadores es modificado por algún medio externo (Funde et al, 2019). Mención aparte merecen los Rovers (Ellery, 2016), que son vehículos destinados a la exploración planetaria que utilizan mecanismos poliarticulados como el llamado Rocker-bogie que pudieran estar combinados con sistemas de suspensión activa (Cordes et al, 2018) o pasiva (Yang et al, 2018).…”