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We present a Gaussian process algorithm for learning the configuration space of a robot subject to holonomic task constraints. Given an observed data set of points that lie on this task-constrained configuration space, or constraint manifold, a point-to-manifold distance function is constructed that measures the distance of any given point from the constraint manifold. The observed data are first...
This article proposes an emotive lifelike robotic face, called ExpressionBot, that is designed to support verbal and non-verbal communication between the robot and humans, with the goal of closely modeling the dynamics of natural face-to-face communication. The proposed robotic head consists of two major components: 1) a hardware component that contains a small projector, a fish-eye lens, a custom-designed...
We have developed two different configurations of series elastic actuators to be used in the lower body of THOR, a full scale humanoid developed for the DARPA Robotics Challenge. Both designs utilize a ball screw transmission but use different output mechanisms. The THOR-Linear actuator uses a simple lever output while the THOR-Hoekens actuator uses a novel inversion of a Hoekens Linkage. The simpler...
Using machine learning algorithms to improve imperfect modeling and to estimate parameters with the hardware in the loop is a promising way to achieve balanced and dynamic gaits. Similar to the pendulum-cart model, a biped can accelerate its center of mass and control its angular momentum by modifying its step size to maintain balance. Using this simple concept, we derive a gradient function and use...
Team ViGIR entered the 2013 DARPA Robotics Challenge (DRC) with a focus on developing software to enable an operator to guide a humanoid robot through the series of challenge tasks emulating disaster scenarios. We designed our operator control station (OCS) to allow multiple operators to request and share information as needed to maintain situational awareness under bandwidth constraints, while directing...
This video presents early results for dynamic balancing on unstable terrain using THOR, a 34-DoF torque-controlled humanoid. The proposed stance controller stabilizes the centroidal dynamics by regulating the Divergent Component of Motion (DCM) using whole-body momentum control. A quadratic program (QP) is used to compute optimal joint torques given desired task-space objectives and frictional contact...
This paper presents a novel method for controlling a dual arm robot to pick heavy objects. The motivation for this study is inspired from the observation of human motion in their daily activities. Two reflex actions are proposed in this work. The first reflex is designed to control the COM of the robot when its stability is endangered by the effect of the object weight. Static stability criterion...
This paper presents a study that compares a humanoid robotic tutor to a human tutor when instructing school children to build a LEGO house. A total of 27 students, between the ages of 11–15, divided into two groups, participated in the study and data were collected to investigate the participants' success rate, requests for help, engagement, and attitude change toward robots following the experiment...
This paper introduces the design tuning of a recently introduced compliant actuation scheme that was developed to provide large energy storage capacity and demonstrate energetic efficient operation. The joint is based on an asymmetric compliant antagonistic actuation scheme where torques from two motors are transmitted to the joint through two elastic elements of different stiffness level and energy...
Biped running can be conceptually reduced to a set of simple and quasi-independent tasks such as weight bearing, upper-body balancing, and energy injection through ankle push-off. We show in this paper that by appropriately designing multi-articular elastic actuators for biped robots in a manner inspired by human biomechanics, these tasks can be favorably expressed in a set of coordinates, in which...
Tool-use is one of the most complex object manipulation abilities of humans and robots. In this paper, we present strategies for implementing tool-use with anthropomorphic service robots. Based on the observation that human tools are specifically designed for the human body, we augment tools with handles that adapt the tool to the specifics of our robot. We develop methods for perceiving the tools...
In this work, a multi-sensor controller to open recipients with screwed caps is presented. A humanoid torso is used to perform the task, first grabbing and holding the target object with one hand and then removing the cap with the other hand. The approach consists of a global controller composed of several modules: object segmentation, grasp synthesis, grasp execution and cap unscrew controller. The...
Supporting somebody while standing up from a seated position is one of the most frequent tasks envisaged for a humanoid assistant used in order to help somebody with reduced mobility around the house. The safest way to do this for a human carer has been clearly defined in patient handling guides for hospitals where a policy of never lifting the patient is strongly recommended. Based on these guidelines,...
This paper discusses a motion planning method for assembling a ring-shaped elastic part to a cylindrical part by using a dual-arm manipulator. When assembling a ring-shaped elastic part, it is important to keep the amount of elastic deformation as small as possible during the assembly task. To achieve this purpose, we show that it is effective to utilize the Covariant Hamiltonian Optimization and...
Despite some prematurely optimistic claims, the ability of robots to grasp general objects in unstructured environments still remains far behind that of humans. This is not solely caused by differences in the mechanics of hands: indeed, we show that human use of a simple robot hand (the Pisa/IIT SoftHand) can afford capabilities that are comparable to natural grasping. It is through the observation...
We present a probabilistic learning framework to form object hypotheses through interaction with the environment. A robot learns how to manipulate objects through pushing actions to identify how many objects are present in the scene. We use a segmentation system that initializes object hypotheses based on RGBD data and adopt a reinforcement approach to learn the relations between pushing actions and...
This paper studies the effects of hand contact force on the stability of a planar humanoid robot while translational perturbations are applied to its foot. A momentum based controller is used to control the robot's motion during the perturbations. Simulation results show that the displacements of the center of pressure (CoP) of the foot decrease substantially when there is a supportive contact between...
In this paper, we present a novel approach towards the integration of visual attention, object based attention and object recognition. Our system is scalable in regard to the required framerate or usage of computational power. Therefore, it is perfectly suited for robotic applications, where time is a crucial factor. We enhance and evaluate our previously presented visual attention system based on...
We propose a new biped locomotion planning method that optimizes locomotion speed subject to friction constraints. For this purpose we use approximate models of required coefficient of friction (RCOF) as a function of gait. The methodology is inspired by findings in human gait analysis, where subjects have been shown to adapt spatial and temporal variables of gait in order to reduce RCOF in slippery...
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