scholarly journals Development and multiple mode control of modular and reconfigurable robot

2021 ◽  
Author(s):  
Hongwei Zhang
Keyword(s):  
Noise Immunity ◽  
Joint Torque ◽  
Hysteresis Phenomenon ◽  
Harmonic Drive ◽  
Active Mode ◽  
Unstructured Environments ◽  
Mode Control ◽  
Multiple Mode ◽  
Torque Estimation ◽  
Reconfigurable Robot

There is a strong desire for robots to manipulate in uncontrolled environments. In uncontrolled environments, the robot has to adapt to the world consisting of only partially known or unknown objects and tasks, and real-time constraints. The capability of robots working in active or passive modes and switching between them helps enabling the robots to work in unstructured environments. Joint torque sensing is essential for implementing multiple mode control of robots. Though there have been a number of means of joint torque sensing, the existing joint sensing techniques have diverse limitations, such as in installation, reliability, cost, and noise immunity. This dissertation work develops a new joint torque sensing method for a modular and reconfigurable robot (MRR) with harmonic drive joints and provides solutions to multiple mode control of MRR based on the proposed sensing technique. This research consists of two main parts. In the first part, a novel mathematical model for compliance of harmonic drives has been proposed. The proposed model captures not only the nonlinear stiffness but also the hysteresis phenomenon of harmonic drive transmission. Based on the developed harmonic drive compliance model, a joint torque estimation method using position measurements is developed. Torque estimation using position measurements provides an advantage of noise immunity to the estimated joint torque. Using the compliance of harmonic drives instead of an additional elastic component does not change the joint dynamics. Building upon the new torque estimation technique, a multiple working mode control algorithm for MRR is developed and experimentally validated. The objective of the second part is to make the wrist suitable for dexterous manipulation in unstructured environments, such as door opening. A robust adaptive controller is developed for tracking control of the wrist in active mode; and a new interactive force compensation technique is proposed based on force sensor measurement, enabling passive working mode of the compact wrist without using mechanical solutions, which not only saves weight and volume, but also avoids losing tracking of the joints’ position when switching from passive mode to active mode. Experiments on a prototype wrist have demonstrated the effectiveness of the proposed method.

scholarly journals Development and multiple mode control of modular and reconfigurable robot

2021 ◽  
Author(s):  
Hongwei Zhang
Keyword(s):  
Noise Immunity ◽  
Joint Torque ◽  
Hysteresis Phenomenon ◽  
Harmonic Drive ◽  
Active Mode ◽  
Unstructured Environments ◽  
Mode Control ◽  
Multiple Mode ◽  
Torque Estimation ◽  
Reconfigurable Robot

There is a strong desire for robots to manipulate in uncontrolled environments. In uncontrolled environments, the robot has to adapt to the world consisting of only partially known or unknown objects and tasks, and real-time constraints. The capability of robots working in active or passive modes and switching between them helps enabling the robots to work in unstructured environments. Joint torque sensing is essential for implementing multiple mode control of robots. Though there have been a number of means of joint torque sensing, the existing joint sensing techniques have diverse limitations, such as in installation, reliability, cost, and noise immunity. This dissertation work develops a new joint torque sensing method for a modular and reconfigurable robot (MRR) with harmonic drive joints and provides solutions to multiple mode control of MRR based on the proposed sensing technique. This research consists of two main parts. In the first part, a novel mathematical model for compliance of harmonic drives has been proposed. The proposed model captures not only the nonlinear stiffness but also the hysteresis phenomenon of harmonic drive transmission. Based on the developed harmonic drive compliance model, a joint torque estimation method using position measurements is developed. Torque estimation using position measurements provides an advantage of noise immunity to the estimated joint torque. Using the compliance of harmonic drives instead of an additional elastic component does not change the joint dynamics. Building upon the new torque estimation technique, a multiple working mode control algorithm for MRR is developed and experimentally validated. The objective of the second part is to make the wrist suitable for dexterous manipulation in unstructured environments, such as door opening. A robust adaptive controller is developed for tracking control of the wrist in active mode; and a new interactive force compensation technique is proposed based on force sensor measurement, enabling passive working mode of the compact wrist without using mechanical solutions, which not only saves weight and volume, but also avoids losing tracking of the joints’ position when switching from passive mode to active mode. Experiments on a prototype wrist have demonstrated the effectiveness of the proposed method.

A Torque Measuring Method for Robot Joints with Harmonic Drives

2013 ◽  
Vol 694-697 ◽  
pp. 981-986 ◽  
Author(s):  
Xi Nan Pan ◽  
Hong Guang Wang ◽  
Yong Jiang
Keyword(s):  
Output Signal ◽  
Measuring Method ◽  
High Accuracy ◽  
Joint Torque ◽  
Harmonic Drive ◽  
Torque Measurement ◽  
First Order ◽  
Tuning Method ◽  
Reconfigurable Robot ◽  
The Relationship

To meet the demand of joint torque measurement for a modular reconfigurable robot, a harmonic drive built-in torque measuring method was proposed. The robot and its joint module and the torque measuring principle were introduced. Based on the two-order ripple model, strains on the flexspline were then analyzed. A new measuing method based on double compensations was proposed. This method cancels out the first order ripples by individual channels, and then cancels out the remain ripples by weighted stacking the signals. The relationship between output signal and torque was given, and a new gain-tuning method was presented. Finally, a simulation was conducted. The simulation proves that the proposed torque measuring method is correct and of high accuracy.

scholarly journals Power efficiency estimation based health monitoring and fault detection of modular and reconfigurable robot

2021 ◽  
Author(s):  
Jing Yaun
Keyword(s):  
Fault Detection ◽  
Health Monitoring ◽  
Power Efficiency ◽  
Joint Torque ◽  
Robot System ◽  
Operation Conditions ◽  
Efficiency Estimation ◽  
Joint Torque Sensor ◽  
Reconfigurable Robot ◽  
Critical Components

Power efficiency degradation of machines often provides intrinsic indication of problems associated with their operation conditions. Inspired by this observation, in this thesis work, a simple yet effective power efficiency estimation base health monitoring and fault detection technique is proposed for modular and reconfigurable robot with joint torque sensor. The design of the Ryerson modular and reconfigurable robot system is first introduced, which aims to achieve modularity and compactness of the robot modules. Critical components, such as the joint motor, motor driver, harmonic drive, sensors, and joint brake, have been selected according to the requirement. Power efficiency coefficients of each joint module are obtained using sensor measurements and used directly for health monitoring and fault detection. The proposed method has been experimentally tested on the developed modular and reconfigurable robot with joint torque sensing and a distributed control system. Experimental results have demonstrated the effectiveness of the proposed method.

scholarly journals Multiple Working Mode Based Door Opening Control and Fault Detection of Mobile Modular and Reconfigurable Robot

2021 ◽  
Author(s):  
Saleh Ahmad Ali
Keyword(s):  
Fault Detection ◽  
Control Design ◽  
Torque Control ◽  
Experimental Results ◽  
Joint Torque ◽  
Detection Scheme ◽  
Door Opening ◽  
Position Errors ◽  
Internal Forces ◽  
Reconfigurable Robot

The study in this thesis addresses the problem of opening a door with a modular and reconfigurable robot (MRR) mounted on a wheeled mobile robot platform. The foremost issue with door opening problems is the prevention of occurrence of large internal forces that arise due to position errors or imprecise modeling of the robot or its environment, i.e. the door parameters, specifically. Unlike previous methods that relied on compliance control, making the control design rather complicated, this thesis presents a new concept that utilizes the multiple working modes of the MRR modules. The control design is significantly simplified by switching selected joints of the MRR to work in passive mode during door opening operation. As a result, the occurrence of large internal forces is prevented. Different control schemes are used for control of the joint modules in different working modes. For passive joint modules, a feedforward torque control approach is used to compensate the joint friction to ensure passive motion. For the active joint modules, a distributed control method, based on torque sensing, is used to facilitate the control of joint modules working under this mode. To enable autonomous door opening, an online door parameter estimation algorithm is proposed on the basis of the least squares method; and a path planning algorithm is developed on the basis of Hermite cubic spline functions, with consideration of motion constraints of the mobile MRR. The theory is validated using simulations and experimental results, as presented herein. A distributed fault detection scheme for MRR robots with joint torque sensing is also proposed in this thesis. The proposed scheme relies on filtering the joint torque command and comparing it with a filtered torque estimate that is derived from the nonlinear dynamic model of MRR with joint torque sensing. Common joint actuator faults are considered with fault detection being performed independently for each joint module. The proposed fault detection scheme for each module does not require motion states of any other module, making it an ideal modular approach for fault detection of modular robots. Experimental results have attested the effectiveness of the proposed fault detection scheme.

Random Lasers: Active Mode Control and Gating

2013 ◽  
Vol 24 (12) ◽  
pp. 29
Author(s):  
Marco Leonetti ◽  
Claudio Conti ◽  
Cefe López
Keyword(s):  
Random Lasers ◽  
Active Mode ◽  
Mode Control
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