The series elastic gripper design, object detection and recognition by touch

2021 ◽  
pp. 1-33
Author(s):  
Ozan Kaya ◽  
Gokce Burak Taglioglu ◽  
Seniz Ertugrul

Abstract In recent years, robotic applications have been improved for better object manipulation and collaboration with human. With this motivation, the detection of objects has been studied with serial elastic parallel gripper by simple touching in case of no visual data available. A series elastic gripper, capable of detecting geometric properties of objects is designed using only elastic elements and absolute encoders instead of tactile or force/torque sensors. The external force calculation is achieved by employing an estimation algorithm. Different objects are selected for trials for recognition. A Deep Neural Network model is trained by synthetic data extracted from STL file of selected objects . For experimental set-up, the series elastic parallel gripper is mounted on a Staubli RX160 robot arm and objects are placed in pre-determined locations in the workspace. All objects are successfully recognized using the gripper, force estimation and the DNN model. The best DNN model capable of recognizing different objects with the average prediction value ranging from 71% to 98%. Hence the proposed design of gripper and the algorithm achieved the recognition of selected objects without need for additional force/torque or tactile sensors.

2011 ◽  
Vol 08 (03) ◽  
pp. 181-195
Author(s):  
ZHAOXIAN XIE ◽  
HISASHI YAMAGUCHI ◽  
MASAHITO TSUKANO ◽  
AIGUO MING ◽  
MAKOTO SHIMOJO

As one of the home services by a mobile manipulator system, we are aiming at the realization of the stand-up motion support for elderly people. This work is charaterized by the use of real-time feedback control based on the information from high speed tactile sensors for detecting the contact force as well as its center of pressure between the assisted human and the robot arm. First, this paper introduces the design of the tactile sensor as well as initial experimental results to show the feasibility of the proposed system. Moreover, several fundamental tactile sensing-based motion controllers necessary for the stand-up motion support and their experimental verification are presented. Finally, an assist trajectory generation method for the stand-up motion support by integrating fuzzy logic with tactile sensing is proposed and demonstrated experimentally.


2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Yijun Li ◽  
Taehyun Shim ◽  
Dexin Wang ◽  
Timothy Offerle

The rack force is valuable information for a vehicle dynamics control system, as it relates closely to the road conditions and steering feel. Since there is no direct measurement of rack force in current steering systems, various rack force estimation methods have been proposed to obtain the rack force information. In order to get an accurate rack force estimate, it is important to have knowledge of the steering system friction. However, it is hard to have an accurate value of friction, as it is subject to variation due to operation conditions and material wear. Especially for the widely used column-assisted electric power steering (C-EPAS) system, the load-dependent characteristic of its worm gear friction has a significant effect on rack force estimation. In this paper, a rack force estimation method using a Kalman filter and a load-dependent friction estimation algorithm is introduced, and the effect of C-EPAS friction on rack force estimator performance is investigated. Unlike other rack force estimation methods, which assume that friction is known a priori, the proposed system uses a load-dependent friction estimation algorithm to determine accurate friction information in the steering system, and then a rack force is estimated using the relationship between steering torque and angle. The effectiveness of this proposed method is verified by carsim/simulink cosimulation.


2013 ◽  
Vol 465-466 ◽  
pp. 1375-1379
Author(s):  
Hanafiah Yussof ◽  
Zahari Nur Ismarrubie ◽  
Ahmad Khushairy Makhtar ◽  
Masahiro Ohka ◽  
Siti Nora Basir

This paper presents experimental results of object handling motions to evaluate tactile slippage sensation in a multi fingered robot arm with optical three-axis tactile sensors installed on its two hands. The optical three-axis tactile sensor is a type of tactile sensor capable of defining normal and shear forces simultaneously. Shear force distribution is used to define slippage sensation in the robot hand system. Based on tactile slippage analysis, a new control algorithm was proposed. To improve performance during object handling motions, analysis of slippage direction is conducted. The control algorithm is classified into two phases: grasp-move-release and grasp-twist motions. Detailed explanations of the control algorithm based on the existing robot arm control system are presented. The experiment is conducted using a bottle cap, and the results reveal good performance of the proposed control algorithm to accomplish the proposed object handling motions.


The internal mechanical condition of an excited muscle has been examined by applying quick stretches at various moments after a maximal shock. At the end of the latent period there is an abrupt change of state, the contractile component suddenly becoming capable of bearing a load equal to the maximum tension set up in an isometric tetanus. The intensity of the active state produced by a shock is greatest at the start, is maintained for a time and then declines as relaxation sets in. The properties of the fully active state are defined by the three constants of the characteristic equation relating speed of shortening to load. A muscle consists mechanically of three components: (1) a contractile one, (2) an undamped series elastic one and (3) a parallel elastic one. The complication provided by (3) is avoided by working with small initial loads. The load-extension relation of the series elastic component has been determined. Its extensibility is high at small loads, becoming much less at greater ones. The full isometric force produces an extension in it of about 10% of the muscle’s length. In an isometric tetanus the form of the myogram is fully determined by the characteristic force-velocity relation of the contractile component and the load-extension curve of the series elastic one, the former having to shorten and stretch the latter before an external tension can be manifested. In a twitch there is insufficient time, before relaxation sets in, for the full tension to be developed. When the tension is raised sufficiently by a quick stretch applied early after a shock the contractile component cannot shorten as it would normally and the heat of shortening is absent. The heat of activation is probably a by-product of the process by which the sudden change of state from rest to full activity occurs. When a muscle is subjected to a tension rather greater than it can bear it lengthens slowly; to a tension considerably greater it ‘gives’ or ‘slips’. When a muscle is stretched rapidly a transitory overshoot of tension occurs followed by ‘slip’. During the disappearance of this extra tension heat is produced, as in the ‘cold drawing’ of a wire or thread. An analogous process occurs in relaxation under a load. When two shocks are applied in succession, the second restores the active state to its full intensity, from which it has declined to an extent depending on the interval after the first one. If, under isometric conditions, the series elastic component is still partly stretched at the moment when the second response occurs, the total tension developed is greater. This is the origin of the so-called ‘supernormal phase’ and the basis of the greater tension maintained in atetanic contraction. During a tetanus each shock restores the active state of the muscle to its full intensity. It seems reasonably certain that excitation of a muscle fibre occurs at its surface. It has been suggested that contraction is set up inside by the arrival of some chemical substance diffusing inwards after liberation a t the surface. The onset, however, of full activity occurs so soon after a shock that diffusion is far too slow to account for it. A process, not a substance, must carry activation inwards.


2010 ◽  
Vol 139-141 ◽  
pp. 2622-2625
Author(s):  
Fen Lin

Road friction coefficient is a critical component in traffic safety. The estimation of tire–road friction coefficient at tires allows the control algorithm in vehicle activity system to adapt to external driving conditions. This paper develops a new tire–road friction coefficient estimation algorithm based on tire longitudinal force estimation and tire slip estimation. Vehicle tire longitudinal forces are estimated by sliding mode observer combined with Kalman filter. Based on the tire forces estimation, road friction coefficient is estimated by recursive least squares algorithm (RLS). The test conditions which contain different friction level road are established in ADAMS/Car. The conclusions validate the reliability and efficiency of the proposed method for estimating the friction coefficient in different adhesion level roads. The research also indicates the theory of slip slope can also be reappeared in virtual experiment based on ADAMS.


2014 ◽  
Vol 631-632 ◽  
pp. 937-940
Author(s):  
Fang He ◽  
Hui Zhang ◽  
Bing Bing Li

Due to irregular information flow for NCS (Networked Control System), network delay has performance of random and variability. It reduces system stability, network performance and control performance. This paper focuses on research of predictive algorithm of network delay. Network delay data is obtained in PROFIBUS-DP. Based on network delay data, the ARMA (Auto-Regressive and Moving Average) model of delay is set up. The parameter estimation algorithm of Robust Kalman is used to estimate parameters of proposed ARMA model of network delay. A simulation example is given and verifies efficiency of predictive algorithm proposed.


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