Boundary Torque Research Articles

Investigation of a Cup-Rotor Permanent-Magnet Doubly Fed Machine for Extended-Range Electric Vehicles

This paper investigates a cup-rotor permanent-magnet doubly fed machine (CRPM-DFM) for extended-range electric vehicles (EREVs). The topology and operating principle of the powertrain system based on CRPM-DFM are introduced. Then, the mathematical model of CRPM-DFM is established and the feedback linearization control of CRPM-DFM is given to realize the decoupling control of flux and torque. Moreover, the torque characteristic of CRPM-DFM is analyzed and the load torque boundaries with sinusoidal steady-state solution of CRPM-DFM is deduced. In addition, the MTPA control is derived to improve the efficiency of CRPM-DFM, and the efficiency of CRPM-DFM regarding various operating modes is investigated. Furthermore, the speed optimization strategy of ICE is proposed to reduce fuel consumption. Finally, the driving performance and fuel economy of the powertrain system are verified by simulation.

Feedback Linearization and Maximum Torque per Ampere Control Methods of Cup Rotor Permanent-Magnet Doubly Fed Machine

This paper establishes the state-space model of the cup rotor permanent-magnet doubly fed machine in the synchronous reference frame. The feedback-linearization control method is used to realize the decoupling control of flux and torque. Then, the upper and lower load torque boundaries are solved. Furthermore, to minimize the stator current magnitude of the control machine under a certain torque, the maximum torque per ampere (MTPA) control is derived. Finally, simulation results demonstrate the good decoupling performance of the feedback-linearization control method and the correctness of the load torque boundaries. In addition, the effectiveness and robustness of the proposed control methods are also demonstrated.

A Novel Torque Boundary-Based Model Predictive Torque Control for PMSM Without Weighting Factor

In this article, a novel torque boundary-based model predictive torque control (MPTC) is proposed to improve the torque and flux performance in permanent magnet synchronous motor (PMSM) drives by straightforwardly reducing the corresponding ripples. For this purpose, an optimal sequential list of two voltage vectors is considered as candidate input and the time durations of the two vectors to be applied are determined based on a predefined torque ripple tolerance band. Considering the torque outcomes both at the switching instant and at the end of the control period, the torque can be limited within the upper and lower boundaries of the preset tolerance band during the whole control period. Meanwhile, by monitoring the number of defined valid vector sequences, the torque boundaries can be optimized online. As a result, the torque ripple can be restrained to a fairly small range, and the torque boundary design work is avoided. In addition, according to the predicted torque outcomes of the candidate inputs, a group of vector sequences can be excluded from the control set before optimization, reducing the computation cost. Moreover, due to the preset torque ripple tolerance, the weighting factor in the cost function is eliminated, thereby avoiding the corresponding tuning work. Experimental results are presented to reveal the effectiveness of the proposed strategy.

A Predictive Energy Management Strategy for Hybrid Electric Powertrain With a Turbocharged Diesel Engine

This paper proposes an energy management strategy for a hybrid electric vehicle (HEV) with a turbocharged diesel engine. By introducing turbocharger to the HEV powertrain, air path dynamics of engine becomes extremely complex and critical to engine torque response during transient processes. Traditional strategy that adopts steady-state-map based engine model may not work properly in this situation as a result of its incapability of accurately capturing torque response. Thus, in this paper, a physical-law based air path model is utilized to simulate turbo “lag” phenomenon and predict air charge in cylinder. Meanwhile, engine torque boundaries are obtained on the basis of predicted air charge. A receding horizon structure is then implemented in optimal supervisory controller to generate torque split strategy for the HEV. Simulations are conducted for three cases: the first one is rule-based torque-split energy management strategy without optimization; the second one is online optimal control strategy using map-based engine model; and the third one is online optimal control strategy combining air path loop model. The comparison of the results shows that the proposed third method has the best fuel economy of all and demonstrates considerable improvements of fuel saving on the other two methods.

Choosing Poses for Force and Stiffness Control

In humanoids and other redundant robots interacting with the environment, one can often choose between different configurations and control parameters to achieve a given task. A classic tool to describe specifications of the desired force/displacement behavior in such problems is the stiffness ellipsoid, whose geometry is affected by the choice of parameters in both joint control and redundancy resolution-namely, gains and angles. As is well known, impedance control techniques can regulate gains to realize any desired shape of the Cartesian stiffness ellipsoid at the end-effector, so that robot geometry selection could appear secondary. However, humans do not use this possibility: To control the stiffness of our arms, we predominantly use arm configurations. Why is that, and does it makes sense to do the same in robots? To understand this discrepancy, we provide a more complete analysis of the task-space force/deformation behavior of compliant redundant arms to illustrate why the arm geometry plays a dominant role in interaction capabilities of robots. We introduce the notion of allowable Cartesian force/displacement (“stiffness feasibility”) regions (SFR) for compliant robots with given torque boundaries. We show that different robot configurations modify such regions and explore the role of robot geometry in achieving an appropriate SFR for the task at hand. The novel concepts and definitions are first illustrated in simulations. Experimental results are then provided to verify the effectiveness of the proposed Cartesian force and stiffness control.

Mobility and agility analysis of a multi-legged subsea robot system

This paper presents a unified mathematical framework for the analysis of mobility and agility of a multi-legged subsea robot. The aim of this research is to analyze a dynamic performance on the multi-legged robot in an underwater environment conditions with hydrodynamic forces, seabed friction, gravity, buoyancy, and so on. The dynamic performance is represented by both translational acceleration (mobility) and rotational acceleration (agility) that ensures no slip at each foot of robot under given a robot's configuration, joint torque boundaries, and environment conditions. To analyze the performance, this work includes the derivation of a dynamic equation and a joint torque constraint equation and the establishment of mathematical framework by using its two equations. The dynamic equation is the relationship equation between joint actuator torques and body acceleration, which is derived from subsea robot dynamics and force and acceleration relationship of body and leg. The joint torque constraint equation for ensuring no slip at the contact point is derived from frictional force constraint conditions. In this paper, the resultant accelerations are represented as polytopes through the mathematical framework and given joint torque bounds. To verify the proposed method, the simulations of 4 and 6-legged robots were performed with the consideration of differential pose, environment, and tidal current.

The 3D Eyeball FEA Model with Needle Rotation

Definition of the force and torque boundaries during ophthalmic operations is a vital step towards design and development of robotic solutions for eye surgery. This paper describes the development of an eyeball FEA model. Unlike other eyeball FEA studies, this 3D eyeball model contains all three layers of the inner eye: retina, choroid and sclera. Furthermore the model includes six extra ocular muscles. The intraocular rotation of a needle tool using a trocar during the surgery was also considered in this study. Although variables such as the thickness of the layers and the property of the orbits and the muscles are unique for every individual, the model was developed by introducing some assumptions and constraints for an average eye. However by changing few parameters a modified model suitable for individuals can be generated. The model gives the stress distribution when the needle rotates inside the eyeball. The results of this study will give a numerical understanding of the forces which are needed for ophthalmic operation.

다족 보행 로봇 시스템의 이동성 및 민첩성

This paper presents a method for the acceleration analysis of multi-legged walking robots in consideration of the frictional ground contact. This method is based on both unified dynamic equation for finding the acceleration of a robot's body and constraint equation for satisfying no-slip condition. After the dynamic equation representing relationship between actuator torques and body acceleration, is derived from the force and acceleration relationship between foot and body's gravity center, the constraint equation is formulated to reconfigure the maximum torque boundaries satisfying no-slip condition from given original actuator torque boundaries. From application of the reconfigured torques to the dynamic equation, interested acceleration boundaries are obtained. The approach based on above two equations, is adapted to the changes of degree-of-freedoms of legs as well as friction of ground. And the method provides the maximum translational and rotational acceleration boundaries of body's center that are achievable in every direction without occurring slipping at the contact points or saturating all actuators. Given the torque limits in infinite normsense, the resultant accelerations are derived as a polytope. From the proposed method, we obtained achievable acceleration boundaries of 4-legged and 6-legged walking robot system successfully.

Conjugate boundary method for control law design of anti–skid brake systems

In this study, a new approach named as conjugate boundary method is presented to design the control law of anti–skid brake systems (ABS). Through phase plane analysis, the nonlinear dynamics of ABS are investigated by using a piecewise linear tyre force model. The new concepts of equilibrium brake torque and conjugate boundaries are introduced to analyse the existence and stability of limit cycles, and the global slip tendency in ABS dynamics. Finally, some selected criteria from Guntur and Ouwerkerk's studies are analysed. From the analysis and simulation results, the rules for designing the threshold values for these criteria are suggested and the evaluation of these criteria are also given.