Optimization of physical parameters of an underactuated quadrupedal robot

In this paper, we present the comparison of different optimization algorithms that are used to optimize the parameters of a simulated legged robotic platform. We compare the results obtained by applying different algorithms on the same model and show the relative advantages and disadvantages of these algorithms. The tested algorithms are Particle Swarm Optimization, Binary Coded Genetic Algorithm, Broyden-Fletcher-Goldfrab-Shannon Algorithm and Method of Zoutendijk. We showed that the globally optimal parameter set reduces the total dissipated energy approximately 50% with respect to the reference paremeter set in the literature. The implemented optimization methods can also be applied to other legged platforms to obtain efficient systems without affecting the performance and the stability

Trajectory-Free Motion Planning of an Unmanned Surface Vehicle Based on MPC and Sparse Neighborhood Graph

Unmanned Surface Vehicles (USV) have gained significant attention in military, science, and research applications in recent years. The development of new USV systems and increased application domain of these platforms has necessitated the development of new motion planning methods to improve the autonomy level of USVs and provide safe and robust navigation across unpredictable marine environments. This study proposes a feedback motion planning and control methodology for dynamic fully-and under-actuated USV models built on the recently introduced sparse random neighborhood graphs and constrained nonlinear Model Predictive Control (MPC). This approach employs a feedback motion planning strategy based on sparsely connected obstacle-free regions and the sequential composition of MPC policies. The algorithm generates a sparse neighborhood graph consisting of connected rectangular zones in the discrete planning phase. Inside each node (rectangular region), an MPC-based online feedback control policy funnels the USV with nonlinear dynamics from one rectangle to the other in the network, ensuring no constraint violation on state and input variables occurs. We systematically test the proposed algorithms in different simulation scenarios, including an extreme actuator noise scenario, to test the algorithm’s validity, effectiveness, and robustness

Characterization of Fixed Points of Spring-Mass Model with a Body Govde Eklenmis Yay-Kutle Modelinin Sabit Noktalarinin Karakterizasyonu

© 2020 IEEE.The Spring Loaded Inverted Pendulum (SLIP) template has long been known to be an appropriate model for motion dynamics of legged systems. However, SLIP template does not define the stabilization of upper body which is not negligible in humanoid robotic systems, even though it effectively explains running behaviour in terms of center of mass. In this paper, fixed points of the running motion at different running speeds, heights and trunk angle conditions of a reflexive controller developed on a spring-mass model with body whose center of mass and hip joint do not overlap is investigated. After calculating fixed points of the model by numerical analysis methods, it is found that the subspace defined by fixed points consisted of a onedimensional curve. Then, the interaction between the boundaries of the fixed points on the curve representing the steady state running behavior and the adjustable parameter of the model is observed. This observation allows us to examine which running dynamics coordinates the model parameters affect. The results obtained here can be inferred from the running dynamics of systems with body