Hexa platform as active environment system - mechanics and control

W artykule zaprezentowano aktuator sztywności bazujący na platformie Hexa, który dedykowany jest do zadań sterowania momentem i siłą w aplikacjach z wykorzystaniem manipulatorów przemysłowych. Podejście to jest interesującą alternatywą dla znanych z literatury i obarczonych istotnymi wadami podatnościami pasywnymi i aktywnymi. W pracy zwrócono szczególną uwagę na konstrukcję mechaniczną platformy, do napędu której wykorzystano tanie serwa firmy Hitec, przeznaczone do zastosowań w robotyce. Omówiono proces projektowania platformy zaczynając od strony mechanicznej, poprzez napędy, elektronikę, a kończąc na otwartej architekturze sterowania.In the paper the idea of using variable stiffness actuator was presented. The actuator is based on the Hexa platform (fig. 2) and is dedicated to force/torque control in the industrial manipulator applications. In view of high stiffness of the robots and usually high stiffness of the environment the passive and active compliant devices have to be used, e.g. to protect system against violent force changes. Many serious problems and disadvantages could be found during application of the known compliant systems [8]. These problems could be reduced by using of the variable stiffness actuator. The proposed actuator is an alternative solution and could be used on the manipulator side [9] or on the environment side [10, 11]. Description of using the passive and active compliance elements could found in chapter 2. Details of mechanic end electric construction of variable stiffness actuator with low cost robotic servos from Hitec are presented in chapter 3. Hardware interface (Fig. 3) is shown in the chapter 4 with main properties of the MiRPA (Middleware for Robotic and Process Control Applications) open control architecture system. Using of the MiRPA in rapid control prototyping systems is described in chapter 5. In the Fig. 6 the complete force control setup is presented. Experimental tests demonstrate that the assembly time of the robot tasks is shorter than in classic systems without variable stiffness actuator

Hexa parallel robot control architecture based on SAM7S microcontrollers family

W niniejszym artykule przedstawiono założenia projektowe oraz realizację otwartej architektury sterowania dla równoległego manipulatora Hexa, w oparciu o 32-bitowe mikrokontrolery z rdzeniem ARM7 TDMI. W projekcie sterownika o niewielkich gabarytach, niskim koszcie i wydajności zbliżonej do rozwiązań komercyjnych wzięto pod uwagę wydajność obliczeniową zastosowanych procesorów. Dla uzyskania lepszych osiągów proces sterowania został podzielony na kilka zadań realizowanych przez cztery procesory. Prezentowane wyniki prac mogą posłużyć jako interesujące wskazówki dla projektantów zarówno prostych jak i złożonych systemów sterowania w mechatronice.In this paper was presented assumptions and implementation of Hexa parallel robot control architecture based on 32-bit microcontrollers with ARM7 TDMI core. In developing low-cost controller of small size, and performances similar to commercial solutions the processors capacity was took into account. For better performance process of control was divided into few tasks which were computed on four processors (Fig. 2). Furthermore there was presented implementation of angular position digital controller (Fig. 5) with respect to the noise influence for control quality. The most difficult problem was to find solution of inverse kinematics with respect to the limited processors capacity. Although the direct kinematics in closed-loop architecture is often complex, the inverse kinematics is very simple. In first step the transform matrices which describe transformation from coordinate systems combined with platform to coordinate systems combined with active joints were found. Last step demonstrates how to find angles in every active joint using geometrical method (Fig. 8). Presented results may be used as helpful hints in developing simple or more complex control systems in mechatronics

Integration of inertial sensors with humanoid robots body. Part I

W niniejszym artykule przedstawiono założenia projektowe oraz budowę systemu sterowania ruchem dla robota humanoidalnego Futaba RBT-1. Zaprezentowano wykonany sterownik oparty o mikrokontroler z rdzeniem ARM7, wyposażony w interfejs komunikacji do sterowania serwonapędami cyfrowymi, moduły radiowej wymiany danych oraz zestaw czujników inercyjnych. Ponadto zwrócono uwagę na interesującą metodę wyznaczania wychylenia poruszającego się obiektu względem Ziemi.This paper presents a part of the control system of the humanoid robot Futaba RBT-1. The hardware consists of a microprocessor based controller equipped with a communication interface for digital servos in robot legs. The main parts of the controller are: an ARM microcontroller, a wireless communication module TLX2401 and a Bluetooth. There was chosen an advanced sensor ADIS16362 iSensorŽ which is a complete inertial system that includes a triaxis gyroscope, a triaxis accelerometer and a programmable digital low-pass filter. The robot control system is shown in Fig. 1. In Section 4 the Inertial Navigation System (INS) is described. It uses the data obtained from the accelerometer and gyroscope to calculate the inclination of the robot body in respect to the gravity direction. It is based on "Efficient Orientation Filter" (developed by Dr. Sebastian Madgwick [1]) which despite being computationally efficient gives very good results. Small computational demands allow it to run on a microcontroller with the ARM7 core in real-time which would be difficult with e.g. Extended Kalman Filter. The main control application (described in the second part of this paper) runs on a PC computer. The robot controller radio-communicates with the PC through ISM 2.4GHz radio modules. Furthermore, the controller has a Bluetooth module which enables it to send measurement data for convinient visualisation in the Matlab/Simulink enviroment

Implicit Control

This chapter discusses implicit control for robot manipulators. Although the terminology is not homogeneous in the literature, here we assume that an implicit control is a way to control the force arising when the end effector makes contact with the environment, where the force control loop is closed around inner position/velocity loops. As opposed, an explicit control scheme assumes that the output of the force controller is directly in terms of the motion control actuation variables (torques or forces, depending on the nature of the joints)

Tai Chi for Reducing Dual-task Gait Variability, a Potential Mediator of Fall Risk in Parkinson’s Disease: A Pilot Randomized Controlled Trial

Objectives: To assess the feasibility and inform design features of a fully powered randomized controlled trial (RCT) evaluating the effects of Tai Chi (TC) in Parkinson’s disease (PD) and to select outcomes most responsive to TC assessed during off-medication states. Design: Two-arm, wait-list controlled RCT. Settings Tertiary care hospital. Subjects Thirty-two subjects aged 40–75 diagnosed with idiopathic PD within 10 years. Interventions Six-month TC intervention added to usual care (UC) versus UC alone. Outcome Measures Primary outcomes were feasibility-related (recruitment rate, adherence, and compliance). Change in dual-task (DT) gait stride-time variability (STV) from baseline to 6 months was defined, a priori, as the clinical outcome measure of primary interest. Other outcomes included: PD motor symptom progression (Unified Parkinson’s Disease Rating Scale [UPDRS]), PD-related quality of life (PDQ-39), executive function (Trail Making Test), balance confidence (Activity-Specific Balance Confidence Scale, ABC), and Timed Up and Go test (TUG). All clinical assessments were made in the off-state for PD medications. Results: Thirty-two subjects were enrolled into 3 sequential cohorts over 417 days at an average rate of 0.08 subjects per day. Seventy-five percent (12/16) in the TC group vs 94% (15/16) in the UC group completed the primary 6-month follow-up assessment. Mean TC exposure hours overall: 52. No AEs occurred during or as a direct result of TC exercise. Statistically nonsignificant improvements were observed in the TC group at 6 months in DT gait STV (TC [20.1%] vs UC [−0.1%] group [effect size 0.49; P = .47]), ABC, TUG, and PDQ-39. UPDRS progression was modest and very similar in TC and UC groups. Conclusions: Conducting an RCT of TC for PD is feasible, though measures to improve recruitment and adherence rates are needed. DT gait STV is a sensitive and logical outcome for evaluating the combined cognitive-motor effects of TC in PD