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Here we present a closed-form solution to the continuous time-varying linear-quadratic regulator problem for zero-moment point (ZMP) tracking. This generalizes previous analytical solutions for gait generation by allowing "soft" tracking (with a quadratic cost) of the desired ZMP, and by providing the feedback gains for the resulting time-varying optimal controller. This enables very fast...
This work addresses the problem of whole-body motion planning for a humanoid robot that must execute a certain task in an environment containing obstacles. A randomized planner is proposed that builds a solution by concatenating whole-body motions. Each whole-body motion is generated so as to realize a center of mass (CoM) movement selected from a set of primitives and simultaneously accomplish a...
Momentum control approaches have been successfully applied to balance controllers for humanoid robots due to their integrated controllability of ground reaction force and the center of pressure. In this paper, we introduce a trajectory-free reactive stepping controller using momentum control. The controller is characterized by moving passively in the direction of external pushes without attempting...
This paper proposes applying Fuzzy Sarsa Learning (FSL) algorithm to biped walking controller of a humanoid robot for having a stable walking motion. In order to evaluate stability of the biped walking in the control problem, we have used the Zero Moment Point (ZMP) criterion based on the inverted pendulum model; via this modeling, the stability of biped robot will depends on trunk motion. The FSL...
This paper proposes a framework of generating behavior sequences for robots, especially for humanoid robots, to perform complex tasks. This framework provides a method for the robot to generalize common features of demonstrated behaviors, to store the learned behaviors in the memory system, to construct a behavior graph to describe relationships among learned behaviors, to find and assemble a behavior...
The most common approach used in modeling humanoid robots is to restrict the motion in two different planes, namely the frontal and sagittal plane, thereby using trigonometric expressions and Euler-angles for its description. In this paper some problems of trajectory interpolation and singularity of motion representation are discussed and the dual quaternion representation is used as an alternative...
In this paper, we resolve the issue of stepping over a large obstacle by exploiting the redundancy of pelvis rotation and the versatility of foot trajectories for the humanoids. The control framework consists of a motion pattern that exploits the redundancy of pelvis rotation to enlarge the kinematic workspace, a generic foot trajectory generation which can be modified by a parametric interface to...
This paper presents the method to retarget human motion. The method can evaluate the ability of the preservation of the original characteristics of human motion data. It enables to compute the joint trajectories of the human corresponding with the retargeted ones of the robot at the same time, by utilizing the geometric identification technique. The obtained trajectories of a human are the solution...
This paper presents a novel control method to stabilize the whole-body motion of humanoid robots when climbing vertical ladders and transitioning between ladders and catwalks. In such environments, the body of the robot tends to incline and rotate because of the slippery surfaces. The inclination and rotation may cause the robot to fail to grasp and thus collide with the rungs. The proposed method...
In situations where humanoid robots with constrained posture walk through a narrow space (e.g. manufacturing plants and kitchens), shuffling motions that are stepless and possess wide foot supporting area are effective. One of the difficulties of humanoid's shuffle translations is the load distribution between both feet. If sole loads are not distributed appropriately, the humanoid robot cannot maintain...
The mass parameters of robots influence performances of model-based control and validation of the simulation results. The mass parameters provided by CAD data are usually rough approximation of the true parameters. Therefore several methods for estimation of those parameters have been proposed. Their precision depends on the used motion, called optimal exciting trajectories. This paper describes a...
We present an optimization method to solve coupled redundant inverse kinematics problems and generate trajectories for humanoid robot full-body manipulation. The basic idea of our algorithm is to divide a manipulation task into a series of key postures, generate multiple diverse initial guesses for each key posture, and use optimization to find inverse kinematics solutions based on these initial guesses...
Whole-Body Control methods offer the potential to execute several tasks on highly redundant robots, such as humanoids. Unfortunately, task combinations often result in incompatibilities which generate undesirable behaviors. Prioritization techniques can prevent tasks from perturbing one another but often to the detriment of the lower precedence tasks. For many tasks, static prioritization is not necessary...
Controlling the robot with a permanently-updated optimal trajectory, also known as model predictive control, is the Holy Grail of whole-body motion generation. Before obtaining it, several challenges should be faced: computation cost, non-linear local minima, algorithm stability, etc. In this paper, we address the problem of applying the updated optimal control in real-time on the physical robot....
Although in recent years several studies aimed at the navigation of robots in cluttered environments, just a few have addressed the problem of robots navigating while moving a large or heavy object. This is especially useful when transporting loads with variable weights and shapes without having to change the robot hardware. On one hand, a major advantage of using a humanoid robot to move an object...
We propose a push-recovery strategy to stabilize the robot under unmodelled, large external forces. The strategy integrates Center-Of-Gravity (COG) angular momentum regulator, COG state estimator, and stepping control, which online modifies the trajectories of the COG and the swing leg. Using the centroidal-moment-pivot criterion, the COG angular momentum regulator controls the dynamics of the COG...
This paper presents the contact-consistent elastic strips (CES) framework, a motion planning approach capable of producing complex multi-contact whole-body humanoid behaviors in dynamic environments. Planning multi-contact motions for humanoid robots is known to be non-trivial since it involves aspects of autonomous balancing, obstacle avoidance, ensuring global connectivity of the workspace and concurrent...
This paper presents a trajectory generator for humanoid robots that can simultaneously consider 3D position tracking of the center-of-mass (COM), reactive stepping (foot positions are non-constant), zero-moment-point (ZMP) constraints as well as position constraints.
We introduce a novel notion for lowering the dimensionality of motion planning problems: Irreducibility. Irreducibility of a configuration space trajectory τ means: We cannot find another configuration space trajectory τ′, such that the swept volume of τ′ is included in the swept volume of τ. The main contribution of our work is twofold: First, we show that motion planning in the space of irreducible...
Having human-like motions will make humanoid robots more predictable and safer for the people around them. An effective way to realize this would be to use human motions as reference. Due to different kinematic and dynamic properties between humans and humanoid robots, however, a human motion could be physically infeasible for a robot and cause the robot to fall over. Therefore, it is necessary to...
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