Independent Torque Research Articles

Specific power input and local micromixing times in turbulent Taylor–Couette flow

In the present work, the distribution of the local dissipation rate of turbulent kinetic energy in Taylor–Couette flow was studied with the help of the particle image velocimetry (PIV). The experimental values of dissipation rate are strongly affected by spatial resolution of PIV measurements. Therefore, a reference value of the average specific power input is needed. Such a value was achieved from an independent torque measurement. Using these values it was possible to quantify the true local values of the dissipation rate. The distribution of mixing times in the gap could thus be calculated and was found to become more homogeneous with increasing turbulence intensity.

Lane Keeping Control System with Independent Wheel Torque Control of Micro Electric Vehicle

This paper examines the feasibility of Direct Yaw-moment Control (DYC) in the context of lane keeping system. The DYC, which is generated by differential traction force distribution, is designed with consideration of the road image information to assist the driver's steering maneuver for lane keeping task. Consequently, the controller is designed to regulate the lateral deviation based on the lane marker position acquired via CCD camera with on-board image processing system. The effectiveness of the proposed control system was verified by actual driving test with micro electric vehicle equipped with two independent in-wheel-motors for generating DYC.

Control of two PM linear motors with a single inverter: application to elevator doors

This work considers the control of two PM synchronous motors using a single inverter. The standard approach to the control of a PM synchronous motor is to use a single inverter which provides independent control of the direct and quadrature voltages (and therefore of the direct and quadrature currents) of the motor. Here, an approach is presented that provides independent torque control of two PM synchronous motors using a single inverter. In this approach, the quadrature current of each motor is controlled while it is shown that the direct current is uncontrollable. Both parallel and series connections of the two motors to the single inverter are considered and it is shown how the singularity of the controller can be avoided in each case. The methodology is applied to the control of elevator doors.

Analysis and simulation of a Lorentz-type slotless, self-bearing motor

Abstract A slotless self-bearing motor design is analyzed. The proposed design eliminates the trade-off between motoring torque and bearing force with respect to PM thickness found in many recent designs. Expressions for torque and radial force production are derived, including both control-type forces and destabilizing side-pull forces. The feedback control algorithm and simulated results are also presented. The analysis indicates that: (1) independent torque and bearing force is achieved for a large number of PM pole pairs; (2) the magnitude of both torque and bearing force increases with PM thickness; and (3) the motor is capable of stable operation as long as the winding current phase shift with respect to the PM flux is small.

Three-dimensional Lump-Mass formulation of a catenary riser with bending, torsion and irregular seabed interaction effect

A three-dimensional Lump-Mass formulation of a catenary riser, capable of handling irregular seabed interaction, with bending and torsional stiffness is presented in this paper. This formulation uses only three degrees of translational freedom and one independent torque variable for each computational node. The generality of the present formulation permits static and dynamic analyses of a wide range of offshore-related slender structure systems such as mooring cables, rigid and flexible risers as well as submarine pipelines. Four sets of results are presented for (i) a hanging catenary, (ii) as (i) but subjected to end torsion, (iii) a wire, chain and spring buoy mooring and (iv) a steel catenary riser on an irregular seabed.

Analysis and Simulation of a Lorentz-Type Slotless, Self-Bearing Motor

A slotless self-bearing motor design is analyzed. The proposed design eliminates the trade-off between motoring torque and bearing force with respect to PM thickness found in many recent designs. Expressions for torque and radial force production are derived, including both control-type forces and destabilizing side-pull forces. The feedback control algorithm and simulated results are also presented. The analysis indicates that: (1) independent torque and bearing force is achieved for a large number of PM pole pairs; (2) the magnitude of both torque and bearing force increases with PM thickness; and (3) the motor is capable of stable operation as long as the winding current phase shift with respect to the PM flux is small.

Thermodynamic analysis of a mechatronic pneumatically driven spherical joint

Jointed-member robotic devices (Arthrobots) can benefit from the pneumatic tug-and-twist technology. In particular, two crossed Twistor-pairs provide a flexural spherical joint in the form of a Twistor gimbal-drive. Previous papers have shown that the performance characteristics of both Tuggers and Twistors may be derived from a unique appropriate enthalpy function, which results in open-loop proportional control. This paper develops the Twistor enthalpy H(P, /spl alpha/) based upon independent volume and torque measurements, which fully accounts for pressure-dependent Twistor's stretch and Coulomb torque. This function then provides model equations for mechatronic computer-control of the final spherical joint.

Multi-objective control synthesis: an application to 4WS passenger vehicles

The vehicle dynamics and control play an important role in an automated highway system for passenger cars. This study addresses the problem of designing active controllers for four-wheel-steering (4WS) vehicles. We first obtain a set of linear maneuvering equations representing the four-wheel steering motions and independent wheel torques for lateral/directional plus roll dynamics. We then formulate simultaneous H 2 and H ∞ (sub)-optimal controls with a desired pole assignment via linear matrix inequalities (LMIs). The steering angles are actively controlled by steering wheel commands through the actuator mechanisms for the lateral/directional and roll motions. Further the wheel power and braking are directly controlled by independent torques. Numerical simulations are performed on a complex vehicle model in order to evaluate the vehicle performance (noise and disturbance attenuation), stability, and robustness under a given class of uncertainty. Finally, the presented autopilot controller provides greater maneuverability and improved directional stability for passenger vehicles.

Vector control of a permanent-magnet synchronous motor using AC-AC matrix converter

This paper uses a recently proposed dqo transformation to analyze a permanent-magnet synchronous machine (PMSM) driven by a nine-switch matrix power converter. The matrix transformation used leads to a new equivalent circuit where its parameters are independent of the frequency of the other side to which the circuit is referred. From this equivalent circuit, a set of command algorithms is deduced in order to control, in an independent way, the flux and torque of the machine. It is shown that the control of the gain and the displacement power factor at either set of terminals is dependent only on the choice of the phase angle in the matrix transformation. In order to verify the validity of the proposed algorithms, a full PMSM drive has been simulated with the assumption of perfect switch behavior for the matrix power converter.

Suboptimal control of rigid body motion with a quadratic cost

In this paper we consider the problem of controlling the rotational motion of a rigid body using three independent control torques. Given a quadratic cost we seek stabilizing state feedback controllers which guarantee that all motions starting within a specified bounded set have cost less than a given number; i.e., we seek suboptimal stabilizing controllers. For a special class of cost functions, we present explicit expressions for suboptimal stabilizing controllers yielding a cost arbitrarily close to the infimal cost. For the general case, we present sufficient conditions which guarantee the existence of linear, suboptimal, stabilizing controllers.

STEERING OF 4WD VEHICLES WITH INDEPENDENT WHEEL TORQUE CONTROL

This paper investigates the steering performance of a new configuration of automotive vehicles-4WD vehicles with independent wheel torque control (IWTC). The vehicle model has no steer linkages and a turning manoeuvre can be realised by controlling the wheel torque at each wheel to give a tyre speed differential between the outside and inside tyres. The wheel torque difference between the outside and inside tyres, which controls the tyre velocity difference, is a function of the handwheel angle and the error between the expected yaw rate and the measured yaw rate. In order to control steer stability, a stability compensator for tyre/road adhesion limit is developed and the yaw rate and yaw acceleration are used as control variables. This strategy first evaluates the vehicle stability and then reacts depending on whether the stability criteria is satisfied. The study shows that IWTC vehicles can be well steered by applying the methods developed in this research.

A Global Approach to Vehicle Control: Coordination of Four Wheel Steering and Wheel Torques

Currently, advanced control systems implemented on production ground vehicles have the goal of promoting maneuverability and stability. With proper coordination of steering and braking action, these goals may be achieved even when road conditions are severe. This paper considers the effect of steering and wheel torques on the dynamics of vehicular systems. Through the input-output linearization technique, the advantages of four-wheel steering (4WS) system and independent torques control are clear from a mathematical point of view. A sliding mode controller is also designed to modify driver’s steering and braking commands to enhance maneuverability and safety. Simulation results show the maneuverability and safety are improved. Although the controller design is based on a four-wheel steering vehicle, the algorithm can also be applied to vehicles of different configurations with slight changes.

Spacecraft attitude control and stabilization: Applications of geometric control theory to rigid body models

In this paper, we study the attitude control problem for spacecraft with gas jet or momentum exchange actuators, using the recent nonlinear geometric control theory. We give necessary and sufficient conditions for controllability of the system in the case that the gas jet actuators yield one, two, or three independent torques. In the case of momentum exchange devices, controllability is studied with three independent actuators, and controllability is shown to be impossible with fewer devices. The former conditions with gas jet actuators are presented in three equivalent ways, and an equivalence is established with an earlier condition by Baillieul. The local controllability problem is also studied in the case of gas jet actuators yielding two independent torques. Using these results, an algorithm stabilizing the controllable system around an equilibrium state and trajectory is outlined, as proposed by Hermes. In the situations considered, however, the linearized systems are not controllable.

Irreversibility onset in spin glasses from torque measurements

Improved torque measurements on CuMn and AgMn alloys show a field independent torque onset temperature for fields from 0.5 kG to 9 kG. This result is compatible with mean field transverse freezing (GT line) predictions.