Virtual Sensors For Advanced Controllers In Rehabilitation Robotics

In order to properly control rehabilitation robotic devices, the measurement of interaction force and motion between patient and robot is an essential part. Usually, however, this is a complex task that requires the use of accurate sensors which increase the cost and the complexity of the robotic device. In this work, we address the development of virtual sensors that can be used as an alternative of actual force and motion sensors for the Universal Haptic Pantograph (UHP) rehabilitation robot for upper limbs training. These virtual sensors estimate the force and motion at the contact point where the patient interacts with the robot using the mathematical model of the robotic device and measurement through low cost position sensors. To demonstrate the performance of the proposed virtual sensors, they have been implemented in an advanced position/force controller of the UHP rehabilitation robot and experimentally evaluated. The experimental results reveal that the controller based on the virtual sensors has similar performance to the one using direct measurement (less than 0.005 m and 1.5 N difference in mean error). Hence, the developed virtual sensors to estimate interaction force and motion can be adopted to replace actual precise but normally high-priced sensors which are fundamental components for advanced control of rehabilitation robotic devices.This work was supported in part by the Basque Country Governments (GV/EJ) under grant PRE-2014-1-152, UPV/EHU's PPG17/56 project, Basque Country Governments IT914-16 project, Spanish Ministry of Economy and Competitiveness' MINECO & FEDER inside DPI2017-82694-R project, Euskampus, FIK and Spanish Ministry of Science and Innovation PDI-020100-2009-21 project

Calibration of multicomponent force and moment transducers using uniaxial force standard machines integrated with tilted plates

Traceability of multicomponent force and moment transducers (MCFMTs) is a metrological priority as stated within the document of future strategy 2017-2027 of the Consultative Committee of Mass and Related Quantities of Bureau International des Poids et Mesures (BIPM). In this paper, a calibration system using force standard machines (FSMs) integrated with tilted plates is described. The main advantage of this method is the possibility to apply force and moment components using existing uniaxial FSMs without the necessity to modify them or to develop specific ones. On the other hand, force and moment components cannot be fully independently applied. Expanded uncertainties of the applied side forces and moments are in the order of around 5%, acceptable for several industrial applications. A procedure for the calibration and the uncertainty assessment of MCFMTs is also provided. Calibration results, in terms of main and cross-talk sensitivities, of a six-components transducer are shown. This method is easily implementable and can be adopted to improve the current standard

Multi-Axis Force Sensor for Human–Robot Interaction Sensing in a Rehabilitation Robotic Device

Human–robot interaction sensing is a compulsory feature in modern robotic systems where direct contact or close collaboration is desired. Rehabilitation and assistive robotics are fields where interaction forces are required for both safety and increased control performance of the device with a more comfortable experience for the user. In order to provide an efficient interaction feedback between the user and rehabilitation device, high performance sensing units are demanded. This work introduces a novel design of a multi-axis force sensor dedicated for measuring pelvis interaction forces in a rehabilitation exoskeleton device. The sensor is conceived such that it has different sensitivity characteristics for the three axes of interest having also movable parts in order to allow free rotations and limit crosstalk errors. Integrated sensor electronics make it easy to acquire and process data for a real-time distributed system architecture. Two of the developed sensors are integrated and tested in a complex gait rehabilitation device for safe and compliant control