Development and evaluation of a compact 6-axis force/moment sensor with a serial structure for the humanoid robot foot (original) (raw)

Optimum design method of multi-axis force sensor integrated in humanoid robot foot system

Measurement, 2011

The multi-axis force sensor (MFS) has been extensively adopted in humanoid robot foot to obtain external forces/moments acted on the foot while in locomotion. The precision and comprehensive performances of MFS originally determined by its elastomer structure are significant essentially for humanoid robots to keep balance by detection of external forces/moments during walking motion. The reason for the transmission of coupling-error of structure is analyzed and then the optimum method for the function of objective-optimization of MFS compliance matrix, Finite Element Method (FEM), orthogonal design and range analysis method are all proposed synthetically. In addition, the comprehensive performances of MFS designed by the optimum method are analyzed and elaborated in a concrete design case. Finally, the main indexes of the MFS are verified experimentally through humanoid robot's dynamic walking motion.

The six-component force sensor for measuring the loading of the feet in locomotion

Materials & Design, 1999

This study presents a novel shoe-shape structure, capable of combining two six-axis force sensors placed in the front part and rear part of that structure. Also, the foot is treated as a 1 d.f. rotating articulation between the heel and the toe to simulate the metatarso-phalangeal joints between and the reaction loading of a foot to be directly measured and registered during gait motion. A shoe-shaped structure, having a hinge in its middle place, is worn on the foot of a tester. In addition, a potentiometer is set around the knee of the tester to register the flexion or extension angle between the thigh stick and shank stick during gait motion. Moreover, each component force measured from six-component force sensors and corresponding angle measured from potentiometer are inputted into the LabVIEW data acquisition system to quantitatively measure the reaction loading with respect to their sizes and directions. The novel six-axis force sensor system and its measuring process can be applied not only in clinical gait analysis and diagnosis of the osteopathy, but also in the study of biped walking robots and the development of new shoe types for manufacturing.

Research on calibration system error of 6-axis force/torque sensor integrated in humanoid robot foot

2010

With the fast development of humanoid robot with high intelligence and accuracy, the improvement of comprehensive performance of 6-axis force/toque sensor(F/T sensor) has been constantly emphasized and further put forward to a higher demand. Except that a good proper mechanical design to guarantee the precision of the F/T sensor, the calibration quality is one of the most important factors of influencing the precision of F/T sensor too. The influencing factor of the precision of F/T sensor and system error source have been analysed from the view point of the calibration in this correspondence for the improvement of optimization design of sensor structure and calibration system in order to reduce or eliminate the error effects, which offers the theoretical foundation for improving the comprehensive performance and measurement accuracy of the F/T sensor.

Design and Analysis of Force/Moment Sensor for a Robot

To safely hold an unidentified object by means of an intelligent hand of robot, the hand has to recognize the weight of it. By attaching six-axis Force/Torque (F/T or Force/Moment) sensor to an intelligent robot's hand the weight can be calculated by measuring forces F x , F y and F z. Forces should be measured in order to precisely pull and push an object. To securely grasp an unidentified object with an intelligent robot's gripper, the forces in the gripping direction and in the gravitational direction needs to be detected, but it also requires to perceive the moments to accurately recognize the position of the object in the grippers. A robot joint can be controlled in better way if three forces and three moments exerted at the joint are measured. The available Force/Torque sensors are bulky, not customized and costly. Therefore, it is essential to customize and develop low cost six axis Force/Torque sensor with new appropriate dimensions for an intelligent robot's joints. Six axis Force/Torque sensor is designed using strain gauge. The strain gauges are selected for Aluminium and its working conditions. The sensor design is based on results of parametric analysis done in ANSYS software to obtain the strain values in the measurable range. The analytical results are compared with Finite Element Analysis (ANSYS) results. The percentage error in deviation is 0.75% maximum.

A near-singular, flexure jointed, moment sensitive Stewart platform based force-torque sensor

A force-torque sensor capable of accurate measurement of the three components of externally applied forces and moments is required for force control in robotic applications involving assembly operations. The goal in this paper is to design a Stewart platform based forcetorque sensor at a near-singular configuration sensitive to externally applied moments. In such a configuration, we show an enhanced mechanical amplification of leg forces and thereby higher sensitivity for the applied external moments. In other directions, the sensitivity will be that of a normal load sensor determined by the sensitivity of the sensing element and the associated electronic amplification, and all the six components of the force and torque can be sensed.

The Role of Compliant Elements in Two-Legged Robot’s Foot Model

Journal of Automation, Mobile Robotics and Intelligent Systems, 2015

Proposi on of compliant foot for bipedal robot is introduced and its proper es are inves gated. The foot consists of four compliant elements (spring-damper) mounted to four ver ces of a rectangular frame. The results of robot gait analysis using Zero Moment Point method are shown. ZMP trajectories for rigid and compliant foot are compared and conclusions are formulated. Foot compliance reduces needed for postural stabilizaon compensatory movements of the upper part of the body by those simplifying control methods and construcon. Obtained results will be applied in real prototype of small humanoidal robot. Robot construc on in which proposed foot will be applied is shortly introduced.

Development of a new “6-axis” force connected sensor

19th International Congress of Metrology (CIM2019), 2019

This new sensor project has been initiated mainly in order to take measurements in the field of biomechanics during motions of human bodies. For that, it’s necessary to detect the efforts at the contacts with these human bodies in real situation, such as during working, walking, running, biking and so on. Up to now, most of 6 components force sensors which are used, for instance are sensors with each component measuring device as perfectly as possible decoupled from each other’s. This leads to expansive or very expansive sophisticated sensors. The present sensor is a stand-alone wireless, small sized 6-axis force sensor with a powerful and precise conditioning and acquisition system. The sensitive cell is a raw Stewart mechanical structure (strain-gages based) with, conversely to usual multicomponent sensors, force and moment components not decoupled at all, but optimally coupled. Owing to the powerful numerical capabilities of the sensor, the 6 effective components of a given mecha...

Zero moment point-measurements from a human walker wearing robot feet as shoes

The anthropomorphic biped robot Bip is equipped with sensors for measuring the ground/feet forces in order to localize the center of pressure (CoP) and zero moment point (ZMP). This paper focuses on experimental results regarding the evolution of the ground contact forces, obtained from a human walker wearing the robot feet as shoes. First, one determines the influence of heavy and rigid metallic shoes on the gait of the subject, during experiments carried out on flat ground. Second, the evolution of the contact forces is studied while walking on parallel planes with different elevations (stairs), then one addresses the case where the feet are supported by two nonparallel planes (uneven terrain). The corresponding analysis is founded on the concepts of virtual supporting surface and pseudo-CoP-ZMP introduced in a companion paper, discussing the theoretical aspects of CoP and ZMP (Sardain and Bessonnet, 2004). Beyond the academic contribution, the data analyzed in this paper could constitute an incitement to design truly anthropomorphic feet, for Bip as well as for other biped robots, because all the current robot feet are functionally rather poor.

Humanoids’feet: state of the art & future directions

2022

Robotic feet play a fundamental role in the walking performance of a biped robot. Feet are essential to maintain dynamic stability and to propel the body during walking. They may ensure stability on uneven terrains. Yet, complex feet are seldom used on humanoids. This paper surveys 36 types of robotic feet we found in the literature. We classified them according to strategy, capabilities, structure, number of degrees of freedom, actuation method of ankle and foot, type of actuator, sensorization and type of control. Subsequently, we analyzed the dynamic and static models of flexible feet. We discussed considerations on foot dynamics or kinematics in the robot's whole body control system. We analyzed both active joints control for feet including actuated joints, and control for feet with elastic elements (for example, a rubber layer in the sole). Finally, we present some limitations of robotic feet and possible future developments.