Dynamic trotting on slopes for quadrupedal robots

Abstract

Abstract-Quadrupedal locomotion on sloped terrains poses different challenges than walking in a mostly flat environment. The robot's configuration needs to be explicitly controlled in order to avoid slipping and kinematic limits. To this end, information about the terrain's inclination is required for carefully planning footholds, the pose of the main body, and modulation of the ground reaction forces. This is even more important for dynamic trotting, as only two support legs are available to compensate for gravity and drive a desired motion. We propose a reliable method for estimating the parameters of the terrain quadrupedal robots move on, in the face of limited perception capabilities and drifting robot pose estimates. By fusing inertial measurements, kinematic data from joint encoders and contact information from force sensors, the local inclination can be robustly estimated and used to optimize the contact forces to reduce slippage. The estimated terrain information, namely the pitch and roll angles of the ground plane, is exploited in an extended version of our previous modelbased control approach. Our improved control framework enabled StarlETH, a medium-sized, fully autonomous, torquecontrollable quadrupedal robot, to trot on slopes of up to 21• .

Dynamic Locomotion Through Online Nonlinear Motion Optimization for Quadrupedal Robots

“…The footprint is represented by the location of the feet of the robot. The orientation of the Plan frame is such that it is parallel to the local estimation of the terrain from the contact points [9], while its yaw angle is computed s.t. the x axis is aligned with the reference high-level velocity.…”

Influence of trunk structure on posture transition from quadrupedalism to bipedalism

“…In particular, quadrupedalism, which avoids tumble is suitable for walking over rough terrain [1,2] and dynamic locomotion [3,4]. In the contract, bipedalism is suitable for walking over flat or small convex and concave terrains [5,6], obtaining a higher viewpoint, working in the standing position, or bridging a barrier.…”

“…Conventional bipedal and quadrupedal robots have a rigid body [1][2][3][4][5][6][7][8]11]. However, their transition is significantly influenced by the trunk's large inertia, locus, center of mass, and large acceleration or deceleration during the quick transition.…”

Foot Contact Estimation for Legged Robots in Rough Terrain

“…To this end, controllers have been developed which minimize the tangential forces at the ground contact. [1][2][3][4] These methods require knowledge of the ground surface normal 2 for each foothold supporting the robot. Previous work on legged locomotion on inclined surfaces can be split into reactive and proactive approaches.…”

“…6 Estimating the ground normal during dynamic walking with only two feet in contact with the ground was presented using the history of the footholds. 4 Proactive control strategies have been shown to work on much more challenging terrain, however they require prior knowledge of the terrain. Some assume perfect knowledge of their environment and can plan the footholds accordingly 2 while others use range sensors to reconstruct the terrain online.…”