Tactile sensing transfers complex interactive information in a most intuitive sense. Such a populated set of data from the environment and human interactions necessitates various degrees of information from both modular and distributed areas. A sensor design that could provide such types of feedback becomes challenging when the target component has a nonuniform, agile, high resolution, and soft surface. This paper presents an innovative methodology for the manufacture of novel soft sensors that have a high resolution sensing array due to the sensitivity of ceramic piezoelectric (PZT) elements, while uncommonly matched with the high stretchability of the soft substrate and electrode design. Further, they have a low profile and their transfer function is easy to tune by changing the material and thickness of the soft substrate in which the PZTs are embedded. In this manuscript, we present experimental results of the soft sensor prototypes: PZTs arranged in a four by two array form, measuring 1.5-2.3 mm in thickness, with the sensitivity in the range of 0.07-0.12 of the normalized signal change per unit force. We have conducted extensive tests under dynamic loading conditions that include impact, step and cyclic. The presented prototype's mechanical and functional capacities are promising for applications in biomedical systems where soft, wearable and high precision sensors are needed.
Abstract-The position control of designed 3 PRR flexure based mechanism is examined in this paper. The aims of the work are to eliminate the parasitic motions of the stage, misalignments of the actuators, errors of manufacturing and hysteresis of the system by having a redundant mechanism with the implementation of a sliding mode control and a disturbance observe. x-y motion of the end-effector is measured by using a laser position sensor and the necessary references for the piezoelectric actuators are calculated using the pseudo inverse of the transformation matrix coming from the experimentally determined kinematics of the mechanism. The effect of the observer and closed loop control is presented by comparing the results with open loop control. The system is designed to be redundant to enhance the position control. In order to see the effects of the redundant system firstly the closed loop control for active 2 piezoelectric actuators experiments then for active 3 piezoelectric actuators experiments are presented. As a result, our redundant mechanism tracks the desired trajectory accurately and its workspace is bigger.
A 3-PRR flexure based mechanism which is used as a redundant mechanism providing only x-y micro positioning is designed and controlled in this paper. The aim of this work is to eliminate the unpredictable motions due to manufacturing and assembling errors by implementing sliding mode control (SMC) with disturbance observer (DOB) using piezoelectric actuator models. The system is designed to be redundant to enhance the position control. In order to see the effects of the redundant system firstly the closed loop control is implemented for 2 piezoelectric actuators and the remainder piezoelectric actuator is treated as a fixture. Then the position control is implemented for 3 piezoelectric actuators. As a result, our redundant mechanism tracks the desired trajectory accurately and its workspace is bigger. Finally we have compared the proposed position control with the conventional PID control. It is seen that SMC with DOB gives better results. We have achieved to make the position control of our mechanism, which has unpredictable position errors due to rough manufacturing, assembly, piezoelectric actuator hysteresis etc. The designed 3-PRR flexure mechanism can be used as a micro positioner with the available measurement in the laboratory. Upravljanje gibanjem redundantnog mehanizma temeljenog na savijanju korištenjem piezoelektričnih aktuatora. U radu se projektira sustav mikro-pozicioniranja redundantnog mehanizma baziranog na savijanju TRR konfiguracije zglobova u x-y ravnini. Zadatak upravljanja je eliminirati nepredvidivo gibanje, koje je posljedica pogreške proizvodnje i montaže, korištenjem kliznog režima i obzervera poremećaja te matematičkih modela piezoelektričnih aktuatora. Sustav je projektiran redundantno kako bi se povećale upravljačke mogućnosti. Kako bi se ispitalo ponašanje sustava bez redundancije, najprije je proveden eksperiment upravljanja s uključena dva piezoelektrična aktuatora i fiksiran treći aktuator. Potom je implementirano upravljanje pozicijom uz uključena sva tri aktuatora. Pokazano je da redundancija u sustavu upravljanja rezultira boljim ponašanjem zadane putanje i većim radnim prostorom. Na posljetku smo predloženi sustav upravljanja pozicijom usporedili s PID regulatorom pozicije. Regulator baziran na kliznom režimu rada s uključenim poremećanjnim obzerverom je postigao bolje ponašanje regulacijskog kruga. Ostvareno je upravljanje pozicijom eksperimentalnog postava koje ima nepredvidive pogreške pozicioniranja zbog odstupanja nastalih prilikom proizvodnje i montaže, utjecaja histereze piezoelektričnog aktuatora itd. Projektirani mehanizam TRR konfiguracije može se upotrijebiti za mikro-pozicioniranje korištenjem mjerenja dostupnih u laboratoriju.Ključne riječi: klizni režim rada, upravljanje piezoelektričnim aktuatorima, mehanizam temeljen na savijanju, obzerver
In this paper, we present a novel concept that can enable the human aware control of exoskeletons through the integration of a soft suit and a robotic exoskeleton. Unlike the state-of-the-art exoskeleton controllers which mostly rely on lumped human-robot models, the proposed concept makes use of the independent state measurements concerning the human user and the robot. The ability to observe the human state independently is the key factor in this approach. In order to realize such a system from the hardware point of view, we propose a system integration frame that combines a soft suit for human state measurement and a rigid exoskeleton for human assistance. We identify the technological requirements that are necessary for the realization of such a system with a particular emphasis on soft suit integration. We also propose a template model, named scissor pendulum, that may encapsulate the dominant dynamics of the human-robot combined model to synthesize a controller for human state regulation. A series of simulation experiments were conducted to check the controller performance. As a result, satisfactory human state regulation was attained, adequately confirming that the proposed system could potentially improve exoskeleton-aided applications.
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