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In this letter, we propose a two-stage strategy for optimal control problems of robotic mechanical systems that proves to be more robust, and yet more efficient, than straightforward solution strategies. Specifically, we focus on a simplified humanoid model, represented as a two-dimensional articulated serial chain of rigid bodies, in the tasks of getting up (sitting down) from (to) the supine and...
We present a new method for planning footstep placements for a robot walking on uneven terrain with obstacles, using a mixed-integer quadratically-constrained quadratic program (MIQCQP). Our approach is unique in that it handles obstacle avoidance, kinematic reachability, and rotation of footstep placements, which typically have required non-convex constraints, in a single mixed-integer optimization...
It is in general complex to consider the complete robot dynamics when planning trajectories for bipedal locomotion. We present an approach to trajectory planning, with the classical Linear Inverted Pendulum Model (LIPM), that takes explicit consideration of the unstable dynamics. We derive a relationship between initial state and the control input that ensures the overall system dynamics will converge...
This paper considers the problem of planning the motion of a humanoid robot that must execute a manipulation task, possibly requiring stepping, in environments cluttered by obstacles. The proposed method explores the submanifold of the configuration space that is admissible with respect to the assigned task and at the same time satisfies other constraints, including humanoid equilibrium. The exploration...
Efficient footstep planning for humanoid navigation through cluttered environments is still a challenging problem. Many obstacles create local minima in the search space, forcing heuristic planners such as A* to expand large areas. The goal of this work is to efficiently compute long, feasible footstep paths. For navigation, finding the optimal path initially is often not needed as it can be improved...
In this paper we demonstrate an original equivalence between footstep planning problems, where discrete sequences of steps are searched for, and the more classical problem of motion planning for a 2D rigid shape, where a continuous collision-free path has to be found. This equivalence enables a lot of classical motion planning techniques (such as PRM, RRT, etc.) to be applied almost effortlessly to...
A robust self-consistent humanoid navigation method is proposed. For any given targeted position and orientation, the robot robustly chases them without bankruptcies such as leg-crossing, excess stride and deadlock. The key idea is to define a canonical stance with respect to the target independently from the current configuration, and trace them by each step alternately. It locally prioritizes the...
In our previous work, a random sampling-based footstep planner has been proposed for global biped navigation in environments with local minima or narrow passages. Goal-Probability Threshold (GPT) is a key parameter which controls the convergence rate of the goal-biased non-uniform sampling in this planner. In this paper, a GPT optimization approach is explained. We construct a benchmarking model,...
We consider the task of planning smooth trajectories for robot motion. In this paper we make two contributions. First we present a method for cubic spline optimization; this technique lets us simultaneously plan optimal task-space trajectories and fit cubic splines to the trajectories, while obeying many of the same constraints imposed by a typical motion planning algorithm. The method uses convex...
A three-step planning method is proposed, aiming at the redundancy of DOFs and the complexity of a biped robot's gait planning. The method presents a quick procedure on the planning of robot's walking gait, and it is used in the walking gait planning of a biped robot, the HIT-Robocean. A robot virtual prototype model firstly is set up with the aid of the softwares, namely, Solidworks, Matlab, and...
This paper proposes the kinodynamic gait planning for humanoid robots where both kinematics and dynamics of the system are considered. We can simultaneously plan both the foot-place and the whole-body motion taking the dynamical balance of the robot into consideration. As a dynamic constraint, we consider the differential equation of the robotpsilas CoG. To solve this constraint, we assume two walking...
In this paper, we propose a method of sensing outdoor environments for a walking and climbing robot. The proposed method ensures the realtime perception of the surface geometry by integrating a range and a gyroscope with a novel arrangement of the sensors. In addition, a gait planning algorithm based on the sensing method is presented. The algorithm runs fast since it is simple, and the rich information...
In this paper, we present a new method that uses random search for online planning of biped walking, given a feasible footstep plan. The Linear Inverted Pendulum dynamic model and the Zero Moment Point concept are employed to solve the walking problem. We consider walk planning as the choice of a sequence of ZMPs leading to a stable walk that satisfies all the dynamic and mechanical constraints of...
A non-time reference gait planning method is proposed. The usual reference variable, time, is substituted by a non-time variable in gait, so the whole gait-planning phase can be divided into two phases, (1) planning the space walking path: Taking the forward locomotion of upper-body as reference variable, considering the constraint of the environment, the walking path of a robot without collision...
The infant-size humanoid robot THBIP-II, Tsinghua University biped robot II, is the second generation prototype of Tsinghua biped robots. THBIP-II is 75 cm tall, weighs 18 Kg, and has 24 degrees of freedom (DOF). This paper addresses the design, mechanical modeling, gait planning method, and global footstep planning method of the robot. First the humanoid mechatronics system and its kinematics and...
Navigation planning for legged robots via foot placement planning has enabled several humanoids to traverse interesting environments autonomously. In this paper we explore methods of adapting foot placement actions to the terrain during the search process, allowing for fuller use of the robot's capabilities, and better resulting paths. We show the results of these adaptive action models for both the...
Biped robots have higher capabilities than other mobile robots, for moving on uneven environments. However, due to natural instability of these robots, their motion planning and control become a more important and challenging task. This article, will present a Cartesian approach for gate planning and control of biped robots without needing to use the joint space trajectories and the inverse kinematics...
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