Non-Overshooting Force Control of Series Elastic Actuators

2010 ◽  
Vol 166-167 ◽  
pp. 421-426
Author(s):  
Ozan Tokatli ◽  
Volkan Patoglu
Keyword(s):  
Force Control ◽  
Position Control ◽  
Force Sensor ◽  
Force Sensors ◽  
Element Orders ◽  
Interaction Forces ◽  
Controlled Systems ◽  
Important Challenge ◽  
Mechanical Devices ◽  
Series Elastic

Whenever mechanical devices are used to interact with the environment, accurate control of the forces occurring at the interaction surfaces arises as an important challenge. Traditionally, force controlled systems utilize stiff force sensors in the feedback loop to measure and regulate the interaction forces. Series elastic actuation (SEA) is an alternative approach to force control, in which the deflection of a compliant element (orders of magnitude less stiff than a typical force sensor) placed between motor and the environment is controlled to regulate the interaction forces. The use of SEAs for force control is advantageous, since this approach possesses inherent robustness without the need for high-precision force sensors/actuators and allows for the accurate control of the force exerted by the actuator through position control of the deflection of a compliant coupling element. Here, a non-overshooting force controller is proposed to be embedded into the control structure of SEAs. Such controller architecture ensures safe operations of SAEs by making sure that the force applied to the environment are always bounded from above by the reference forces commanded to the controller.

Optimal Design of a Micro Series Elastic Actuator

2010 ◽  
Author(s):  
Ozan Tokatli ◽  
Volkan Patoglu
Keyword(s):  
Optimal Design ◽  
Force Control ◽  
Pareto Front ◽  
Position Control ◽  
Compliant Mechanism ◽  
Tracking Error ◽  
Movement Direction ◽  
Design Criteria ◽  
Coupling Element ◽  
Series Elastic

We propose using series elastic actuation (SEA) in micro mechanical devices to achieve precise control of the interaction forces. Using μSEA for force control removes the need for high-precision force sensors/actuators and allows for accurate force control through simple position control of the deflection of a compliant coupling element. Since the performance of a μSEA is highly dependent on the design of this compliant coupling element, we employ a design optimization framework to design this element. In particular, we propose a compliant, under-actuated half-pantograph mechanism as a feasible kinematic structure for this coupling element. Then, we consider multiple design objectives to optimize the performance of this compliant mechanism through dimensional synthesis, formulating an optimization problem to study the trade-offs between these design criteria. We optimize the directional manipulability of the mechanism, simultaneously with its task space stiffness, using a Pareto-front based framework. We select an optimal design by studying solutions on the Pareto-front curve and considering the linearity of the stiffness along the actuation direction as a secondary design criteria. The optimized mechanism possesses high manipulability and low stiffness along the movement direction of the actuator; hence, achieves a large stroke with high force resolution. At the same time, the mechanism has low manipulability and high stiffness along the direction perpendicular to the actuator motion, ensuring good disturbance rejection characteristics. We model the behavior of this compliant mechanism and utilize this model to synthesize a controller for μSEA to study its dynamic response. Simulated closed loop performance of the μSEA with optimized coupling element indicates that force references can be tracked without significant overshoot and with low tracking error (about 1.1%) even for periodic reference signals.

Force Control System for Autonomous Micro Manipulation

2002 ◽  
Vol 14 (3) ◽  
pp. 212-220 ◽  
Author(s):  
Tamio Tanikawa ◽  
◽  
Masashi Kawai ◽  
Noriho Koyachi ◽  
Tatsuo Arai ◽  
...  
Keyword(s):  
Control System ◽  
Force Control ◽  
Position Control ◽  
Force Sensor ◽  
Microscopic Object ◽  
Object A ◽  
Force Control System ◽  
Grasping Force ◽  
Micro Surgery ◽  
Micro Force Sensor

A dexterous micro manipulation system was developed for applications such as assembling micro machines, manipulating cells, and micro surgery. We have proposed a concept of a two-fingered micro hand, designed and built a prototype. We succeeded in performing basic micro manipulations with a teleoperation, including the grasp, release, and rotation of a microscopic object. The micro hand is controlled with a position control only. An operator has to guess a micro grasping force on the object from a microscope image. The accurate micro manipulation depends on a skill of the operator yet. For an easy manipulation and an automatic manipulation, it is necessary to measure the micro forces between the finger and the object. A micro force sensor has developed for a force control in micro manipulation on a corroboration research of AIST and Olympus Optical Co., Ltd. Its resolution is 0.5 nN in theoretically. In this paper, we will mention the micro force sensor and to perform an automatic micro manipulation with installing the sensor and a force control system. Basic experiment shows excellent micro capability.

scholarly journals A Sliding Mode Force and Position Controller Synthesis for Series Elastic Actuators

Robotica ◽  
2019 ◽  
Vol 38 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Emre Sariyildiz ◽  
Rahim Mutlu ◽  
Haoyong Yu
Keyword(s):  
Force Control ◽  
Dynamic Models ◽  
Position Control ◽  
Sliding Mode ◽  
Dynamic Environment ◽  
Industrial Robots ◽  
Motion Controller ◽  
Mismatched Disturbances ◽  
Series Elastic Actuators ◽  
Series Elastic

SummaryThis paper deals with the robust force and position control problems of series elastic actuators (SEAs). It is shown that an SEA’s force control problem can be described by a second-order dynamic model which suffers from only matched disturbances. However, the position control dynamics of an SEA is of fourth order and includes matched and mismatched disturbances. In other words, an SEA’s position control is more complicated than its force control, particularly when disturbances are considered. A novel robust motion controller is proposed for SEAs by using disturbance observer (DOb) and sliding mode control. When the proposed robust motion controller is implemented, an SEA can precisely track desired trajectories and safely contact with an unknown and dynamic environment. The proposed motion controller does not require precise dynamic models of environments and SEAs. Therefore, it can be applied to many different advanced robotic systems such as compliant humanoids, industrial robots and exoskeletons. The validity of the proposed motion controller is experimentally verified.

Optimal assembly of a skin panel onto the fuselage framework based on force control technology

2016 ◽  
Vol 230 (6) ◽  
pp. 447-451
Author(s):  
Fengfeng Wu ◽  
Dongsheng Li ◽  
Baorui Du
Keyword(s):  
Force Control ◽  
Position Control ◽  
Distance Measure ◽  
Control Method ◽  
Force Sensor ◽  
Small Samples ◽  
Control Technology ◽  
Element Analysis ◽  
Degree Of Confidence ◽  
Size Interval

It is important for fuselage assembly to align the skin panel onto the frame, i.e. to reduce the gaps and subsequently lessen the need for shimming, but conventional position control method cannot always meet the requirement. This study proposed a direct force control technology, which can be directly promoted to a full-rate production without making any dedicated assistance and complex finite element analysis. This strategy was based on a force sensor mounted on a flexible tooling locator to feed back the pressing force information to the controller system. To achieve a certain compressing status, the system was controlled to achieve a desired force rather than reach a specific position. After obtaining four ideal force values from an experimental study during a prototype trial-production, a force-size interval that provides a certain grey degree of confidence was proposed for the flexible tooling control system using a parameter estimation approach for small samples based on the grey distance measure. Compared with conventional position control method, force control technology can achieve better compressing status, since it enables a reduction of all gap values between the skin panel and the framework by 0.15 mm on average or even 0.2 mm at most in the same assembly process.

Research on Velocity Servo-Based Hybrid Position/Force Control Scheme for a Grinding Robot

2012 ◽  
Vol 490-495 ◽  
pp. 589-593 ◽  
Author(s):  
Qing Wei Zhang ◽  
Li Li Han ◽  
Fang Xu ◽  
Kai Jia
Keyword(s):  
Force Control ◽  
Feedback Loop ◽  
Force Feedback ◽  
Position Control ◽  
Force Sensor ◽  
Robot Controller ◽  
Control Scheme ◽  
Exact Position ◽  
Grinding Tool ◽  
Data Signal

In this paper, a velocity servo-based hybrid position/force control scheme for a grinding robot is presented. It simultaneously performs stable force control and exact position control along curved surface for a grinding robot. The force feedback loop changing the force to velocity, which will be used in the velocity servo-based robot, can control the force directly and has a faster response. The position feedback loop controls the grinding tool in a desired trajectory in Cartesian space. An overview of the control algorithm as well as the force data signal processing and the communication between force sensor and robot controller is described.

scholarly journals Neural Network Based Contact Force Control Algorithm for Walking Robots

Sensors ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 287
Author(s):  
Byeongjin Kim ◽  
Soohyun Kim
Keyword(s):  
Neural Network ◽  
Contact Force ◽  
Force Control ◽  
Control Algorithm ◽  
Position Control ◽  
Linear Quadratic Regulator ◽  
Walking Robots ◽  
Test Model ◽  
Linear Quadratic ◽  
Contact Force Control

Walking algorithms using push-off improve moving efficiency and disturbance rejection performance. However, the algorithm based on classical contact force control requires an exact model or a Force/Torque sensor. This paper proposes a novel contact force control algorithm based on neural networks. The proposed model is adapted to a linear quadratic regulator for position control and balance. The results demonstrate that this neural network-based model can accurately generate force and effectively reduce errors without requiring a sensor. The effectiveness of the algorithm is assessed with the realistic test model. Compared to the Jacobian-based calculation, our algorithm significantly improves the accuracy of the force control. One step simulation was used to analyze the robustness of the algorithm. In summary, this walking control algorithm generates a push-off force with precision and enables it to reject disturbance rapidly.

Research on PVDF Micro-Force Sensor

2014 ◽  
Vol 599-601 ◽  
pp. 1135-1138
Author(s):  
Chao Zhe Ma ◽  
Jin Song Du ◽  
Yi Yang Liu
Keyword(s):  
Power Dissipation ◽  
Polyvinylidene Fluoride ◽  
High Sensitivity ◽  
Force Sensor ◽  
Calibration Method ◽  
Pvdf Film ◽  
Force Sensors ◽  
Low Power Dissipation ◽  
Micro Force Sensor ◽  
Processing Circuit

At present, sub-micro-Newton (sub-μN) micro-force in micro-assembly and micro-manipulation is not able to be measured reliably. The piezoelectric micro-force sensors offer a lot of advantages for MEMS applications such as low power dissipation, high sensitivity, and easily integrated with piezoelectric micro-actuators. In spite of many advantages above, the research efforts are relatively limited compared to piezoresistive micro-force sensors. In this paper, Sensitive component is polyvinylidene fluoride (PVDF) and the research object is micro-force sensor based on PVDF film. Moreover, the model of micro-force and sensor’s output voltage is built up, signal processing circuit is designed, and a novel calibration method of micro-force sensor is designed to reliably measure force in the range of sub-μN. The experimental results show the PVDF sensor is designed in this paper with sub-μN resolution.

Sign in / Sign up

Export Citation Format

Share Document