scholarly journals Reducing Uncertainty Using Placement and Regrasp Planning on a Triangular Corner Fixture

2021 ◽  
Author(s):  
Zhengtao Hu ◽  
Weiwei Wan ◽  
Keisuke Koyama ◽  
Kensuke Harada
Keyword(s):  
High Precision ◽  
Position Control ◽  
Geometric Constraints ◽  
Planning Method ◽  
Experimental Section ◽  
Assembly Tasks ◽  
Low Uncertainty

This paper presented an regrasp planning method to eliminate grasp uncertainty while considering the geometric constraints of a fixture. The method automatically finds the Stable Placement Poses (SPPs) of an object on a Triangular Corner Fixture (TCF), elevates the object from its SPPs to dropping poses and finds the Deterministic Dropping Poses (DDPs), builds regrasp graphs by using the SPP-DDP pairs and their associated grasp configurations, and searches the graph to find regrasp motion sequences for precise assembly. Since the SPPs and their associated regrasps are constrained by the TCF's geometry and have high precision, the final object poses regrasped via it has low uncertainty and can be directly used for assembly by position control. In the experimental section, we study the performance of analytical and learning-based methods for estimating the DDPs of different objects and quantitatively examine the proposed method's ability to suppress uncertainty using assembly tasks like peg-in-hole insertion and sheathing tubes, aligning holes, mounting bearing housings, etc. The results demonstrate the method's robustness and efficacy.

scholarly journals Reducing Uncertainty Using Placement and Regrasp Planning on a Triangular Corner Fixture

2021 ◽  
Author(s):  
Zhengtao Hu ◽  
Weiwei Wan ◽  
Keisuke Koyama ◽  
Kensuke Harada
Keyword(s):  
High Precision ◽  
Position Control ◽  
Geometric Constraints ◽  
Planning Method ◽  
Experimental Section ◽  
Assembly Tasks ◽  
Low Uncertainty

This paper presented an regrasp planning method to eliminate grasp uncertainty while considering the geometric constraints of a fixture. The method automatically finds the Stable Placement Poses (SPPs) of an object on a Triangular Corner Fixture (TCF), elevates the object from its SPPs to dropping poses and finds the Deterministic Dropping Poses (DDPs), builds regrasp graphs by using the SPP-DDP pairs and their associated grasp configurations, and searches the graph to find regrasp motion sequences for precise assembly. Since the SPPs and their associated regrasps are constrained by the TCF's geometry and have high precision, the final object poses regrasped via it has low uncertainty and can be directly used for assembly by position control. In the experimental section, we study the performance of analytical and learning-based methods for estimating the DDPs of different objects and quantitatively examine the proposed method's ability to suppress uncertainty using assembly tasks like peg-in-hole insertion and sheathing tubes, aligning holes, mounting bearing housings, etc. The results demonstrate the method's robustness and efficacy.

Assembly Strategies for Parts with a Plane of Symmetry

Robotica ◽  
1991 ◽  
Vol 9 (2) ◽  
pp. 189-195 ◽  
Author(s):  
N. A. Aspragathos
Keyword(s):  
Large Class ◽  
Position Control ◽  
Hybrid Control ◽  
Robotic System ◽  
Torque Sensor ◽  
Complex Assembly ◽  
Assembly Tasks

SUMMARYThis paper describes the development of assembly strategies based on hybrid force/position control. The assembly strategies developed are confined to the large class of assembly tasks defined as a peg-in-the-hole assembly having a plane of symmetry passing through the axis of insertion.The basic idea to develop a robotic system for programmable assembly is presented. This system can currently operate controlled manipulators with minor modifications, i.e. if a force/torque sensor and proper software for hybrid control are provided.The principles of writing assembly strategies are analysed and examples of more complex assembly tasks than the classic round peg-in-the-hole are discussed in detail.

Stream Selector’s Control System Based on High-Precision Incremental Encoder

2013 ◽  
Vol 303-306 ◽  
pp. 1657-1660
Author(s):  
Zhi Guang Zhang ◽  
Wei Hu ◽  
Xiao Qiong Li ◽  
Xue Fei Lv ◽  
Min Ping Zhang ◽  
...  
Keyword(s):  
Control System ◽  
Power Consumption ◽  
High Precision ◽  
Position Control ◽  
High Reliability ◽  
Dc Motor ◽  
Step Motor ◽  
Low Power Consumption ◽  
Incremental Encoder ◽  
The One

For the precision rotor position control of stream selector, a control system based on direct current motor (DC motor) has been constructed. The DC motor, with a high-precision incremental encoder used as the driving force, was assembled with the stream selector rotor through a shaft coupling. Following the motor rotation, the encoder generated two-channel quadrature pulses and one channel index pulses. An ultralow-power consumption microcontroller (msp430f2232) received theses pulses and calculated them. The position of the slot was determined by the number of pulses counted from the index pulse. Operator can set and monitored the slot positions of five stream selectors simultaneously through the program which was written with LabVIEW on the host computer. This module featured high reliability and low power consumption compared with the one driven by step motor. Beyond that, it was much smaller and lighter.

High-Precision Tracking Control of Machine Tool Feed Drives Based on ADRC

2016 ◽  
Author(s):  
Chengyong Zhang ◽  
Yaolong Chen
Keyword(s):  
Machine Tool ◽  
High Precision ◽  
Tracking Control ◽  
Position Control ◽  
Feedback System ◽  
Pi Controller ◽  
Ball Screw ◽  
Feed Drives ◽  
Precision Tracking ◽  
Precision Tracking Control

In this paper, the active-disturbance-rejection control (ADRC) is applied to realize the high-precision tracking control of CNC machine tool feed drives. First, according to the number of the feedback channel, the feed systems are divided into two types: signal-feedback system, e.g., linear motor and rotary table, and double-feedback system, e.g., ball screw feed drive with a load/table position feedback. Then, the appropriate controller is designed to ensure the closed-loop control performance of each type of system based on the idea of ADRC. In these control frameworks, the extended state observers (ESO) estimate and compensate for unmodeled dynamics, parameter perturbations, variable cutting load, and other uncertainties. For the signal-feedback system, the modified ADRC with an acceleration feedforward term is used directly to regulate the load/table position response. However, for the double-feedback system, the ADRC is applied only to the motor position control, and a simple PI controller is used to achieve the accurate position control of the load. In addition, based on ADRC feedback linearization, a novel equivalent-error-model based feedforward controller is designed to further improve the command following performance of the double-feedback system. The experimental results demonstrate that the proposed controllers of both systems have better tracking performance and robustness against the external disturbance compared with the conventional P-PI controller.

A High-Speed and High-Precision Position Control Using Sliding Mode Compensator

2008 ◽  
Vol 128 (9) ◽  
pp. 1114-1120
Author(s):  
Kazuhiro Tsuruta ◽  
Kazuya Sato ◽  
Nobuhiro Ushimi ◽  
Takashi Fujimoto
Keyword(s):  
High Precision ◽  
High Speed ◽  
Position Control ◽  
Sliding Mode

A sequence planning method for five-axis hybrid manufacturing of complex structural parts

2019 ◽  
Vol 234 (3) ◽  
pp. 421-430
Author(s):  
Changqing Liu ◽  
Yingguang Li ◽  
Sen Jiang ◽  
Zhongyu Li ◽  
Ke Xu
Keyword(s):  
High Precision ◽  
Planning Method ◽  
Hybrid Manufacturing ◽  
Sequence Planning ◽  
Tool Accessibility ◽  
Complex Structural ◽  
Structural Parts ◽  
Five Axis ◽  
Printing Direction ◽  
Complex Structural Parts

The concept of additive–subtractive hybrid manufacturing provides a new idea for the manufacturing of high-precision complex structural parts. Currently, under the five-axis additive–subtractive hybrid manufacturing mode, existing research work concerned with sequence planning issues have limitations. This article presents a sequence planning method for hybrid manufacturing of complex structural parts with high precision. The initial printing direction of parts was determined based on an iterative search method and the initial hybrid manufacturing sequence was constructed by part volume decomposition, which solved the coupling problem of printing direction decision and machinability calculation. Under the constraint of tool accessibility, the whole planning of the hybrid manufacturing sequence was realized based on greedy algorithm. This method has achieved highly effective planning of the alternative sequence in the process of hybrid manufacturing, thus greatly reduced the number of tool changes required and laid a foundation for the realization of highly efficient hybrid manufacturing.

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