Dynamic turning and running of a hexapod robot using a separated and laterally arranged two-leg model

Abstract

We report on the development of separated and laterally arranged two-leg (SLTL) models with/without differentiated leg properties and their use as the dynamic running and turning templates for a hexapod robot. The laterally arranged two-leg morphology enables differential driving for turning. The differentiable leg settings, such as stiffness, enables the model to adopt unbalanced leg arrangements of empirical legged gaits, such as a tripod gait, into consideration. The fixed-point motion of the model was utilized as the main methodology to plan dynamic running and turning, in which the plot of one-step distance versus period was constructed for the legs’ operation point selection and matching. The proposed methodology was experimentally validated using four indices: turning curvature, flight phase, motion stability, and energy efficiency. The experimental results show that the running robot using the SLTL model with differentiated leg stiffness has better energy efficiency than one without by 4%, while the latter model has identical performance to the original spring-loaded inverted pendulum model with rolling contact. As for turning, the robot using the SLTL models with/without differentiated leg stiffness can preserve dynamic turning in all experiments with turning curvatures up to 0.28m^(-1) and 0.30m^(-1), respectively, 33% and 43% more than the robot using the original model-less phase-shift turning strategy (0.21 m^(-1)). Using the proposed model-based strategy, the flight phase of the robot turning in all curvatures (including straight running) maintains around 20%, the root-mean-squared (RMS) values of pitch and roll remains less than 3 deg, and the specific resistance (SR) is bounded between 0.64 and 0.73. By contrast, the robot using the phase-shifting turning strategy can maintain dynamic motion up to a turning curvature of 0.21 m^(-1). A further increase in phase shifting not only does not increase the turning curvature but also changes the robot motion from running to walking. In this case, no flight phase exists, the SR jumps up significantly, and RMS values of pitch and roll also increase dramatically. In short, the experimental validation confirms the effectiveness of the proposed methodology for initiating the dynamic running and turning of the robot.

Development and implementation of a new approach for posture control of a hexapod robot to walk in irregular terrains

“…Deepa et al and Xue et al [6, 7] also studied the locomotion efficiency of a hexapod robot using the dynamic simulation software CoppeliaSim. Using the Euler–Lagrangian dynamic formulation, Chang and Lin [8] presented the study of running and turning gaits for a hexapod with spring-loaded inverted pendulum limbs. The same dynamic formulation is implemented by Chávez and Alcántara [9] in order to evaluate the energy consumption and trajectory of a hexapod walking across a plane.…”

Multi-constraint spatial coupling for the body joint quadruped robot and the CPG control method on rough terrain

“…In this process, the robot has to both climb over different obstacles and constantly adjust its position to adapt to the drastic changes of the terrain, and the dynamic change of the robot can cause its center of gravity (COG) to project outside the area of foothold, which can lead to unstable or even overturn [3]. The quadruped robots should have features such as optimized gait planning algorithms [4], high stability margins [5], and sensitive responses to ensure they can efficiently and quickly complete preset tasks in complex or rough terrain environments, where a stable gait is essential [6]. Currently, legged robots are mainly rigid bodies, and the primary research concerns improving their high dynamicity, environmental adaptability, and large load capacity [7][8][9].…”