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The goal of this study was to determine how individuals post-stroke response to the lateral assistance force applied to the pelvis during treadmill walking. Ten individuals post chronic (> 6 months) stroke were recruited to participate in this study. A controlled assistance force (∼10% of body weight) was applied to the pelvis in the lateral direction toward the paretic side during stance of the...
This paper presents a novel strategy for designing passively adaptive, statically stable walking robots with full body mobility that are exactly constrained and non-redundantly actuated during stance. In general, fully mobile legged robots include a large number of actuated joints, giving them a wide range of controllable foot placements but resulting in overconstraint during stance, requiring kinematic...
Legged robots require a robust and fast responding feet contact detection strategy. Common force sensors are often too heavy and can be easily damaged during impacts with the terrain. Therefore, it is desirable to detect a contact without a force sensor. This paper introduces a probabilistic contact detection strategy which considers full dynamics and differential/forward kinematics to maximize the...
Legged robots such as hexapods have the potential to traverse unstructured terrain. This paper introduces a novel hexapod robot (Weaver) using a hierarchical controller, with the ability to efficiently traverse uneven and inclined terrain. The robot has five joints per leg and 30 degrees of freedom overall. The two redundant joints improve the locomotion of the robot by controlling the body pose and...
We describe the design and hardware implementation of our walking and manipulation controllers that are based on a cascade of online optimizations. A virtual force acting at the robot's center of mass (CoM) is estimated and used to compensated for modeling errors of the CoM and unplanned external forces. The proposed controllers have been implemented on the Atlas robot, a full size humanoid robot...
We introduce a center of mass estimator, and its application in full body inverse dynamics control, fall detection and fall prevention for humanoid robots. We use the Linear Inverted Pendulum Model dynamics with an offset to predict the center of mass motion. This offset can be interpreted as a modelling error on the center of mass position, or an external force exerted on the center of mass of the...
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...
This paper introduces a state estimation methodology for a hexapod robot that makes use of proprioceptive sensors and a kinematic model of the robot. The methodology focuses on providing reliable full pose state estimation for a commercially-available hexapod robot platform with the use of only commonly-available sensors. The presented methodology provides the derivation of the kinematic model and...
In the every expanding field of robotics, mobile robots come in a two primary variations: wheeled and legged. This paper will focus on the latter, specifically a hexapod with a circular body that has its six legs distributed axisymmetrically around the body. The core goal of the project discussed here is to allow the robot to dynamically change foot placement based on an input vector in addition to...
Autonomous wall cutting is described using an Atlas humanoid robot. An integrated wall-cutting skill is presented, which only requires an operator to issue supervisory-level commands to prescribe a desired cutting path, leading to autonomous cutting.
Presented is the design, implementation, and initial gait testing of a lightweight, compliant robotic device for ankle rehabilitation. Many patients with neuromuscular disorders suffer deficits in sensorimotor control of the ankle joint, leading to an abnormal walking pattern. Robotic devices have been used to assist ankle rehabilitation. However, these devices are usually heavy and rigid, which can...
Humanoid robots are currently still far from reaching the impressive human walking capabilities. Among the different methods used to design walking controllers, those based on the Zero-Moment Point (ZMP) criterion are among the most popular, even if they induce intrinsic limitations in terms of energy consumption and robustness. In parallel, bio-inspired controllers are emerging. They overcome the...
This study aims to achieve the smooth going up and down the step for a biped robot whose leg has 6 DOFs with kinematics redundancy. If COG position is not controlled in the going up and down motion, the robot falls down forward or backward. The robot has achieved the motion of going up the step in the proposed approach by its COG out of shifting the waist position. In our proposed approach, the COG...
This paper investigates several robotic mechanisms for ankle function evaluation, measurement and physiotherapy. For the choice, design and operation of the mechanism the kinematics of the foot is described. This is based on a kinematics model of foot adopted from biomechanics literature, under the hypothesis that foot kinematics is similar to that of a 2R serial robot. A 3D scanner and an inertial...
Consider a biped evolving in the sagittal plane. The unexpected rotation of the supporting foot can be avoided by controlling the zero moment point (ZMP). The objective of this study is to propose and analyze a control strategy for simultaneously regulating the position of the ZMP and the joints of the robot. If the tracking requirements were posed in the time domain, the problem would be underactuated...
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