Showing papers on "Dynamic braking published in 1975"

Personal rapid transit system

Abstract: A land transportation system for a vehicle that is supported and guided by air bearings. The vehicle requires no driver or motorman because a guideway determines the direction of travel, except at switch-points in the network. The vehicle is propelled by a linear synchronous motor when on the guideway. The linear synchronous motor primary is embedded in the guideway. A linear inductor alternator provides on-board electric power. A pair of linear induction motors are used to accelerate the vehicle from a station stop up to guideway synchronous speed, to provide a magnetically attractive element to permit switching in guideway tracks, and to provide dynamic braking when stopping at the destination station. No physical contact is required between the guideway and any part of the vehicle while in motion in order to produce tractive effort or for the generation of electric power on board the vehicle to supply auxiliaries such as a motor driving a fan, interior lights, and vehicle-to-wayside communications equipment.

Dynamic braking in controlled current motor drive systems

Abstract: A current source power converter for an electric motor is comprised by a combined controlled rectifier and chopper which is coupled to a controlled-current inverter by a dc reactor. In the motoring mode the combined rectifier and chopper functions as a phase controlled rectifier to control the current magnitude. In the dynamic braking mode a line switch is opened and a braking resistor placed across the rectifier output, and the combined rectifier and chopper is operated as a chopper to control the average voltage across the braking resistor and thus the current magnitude during braking.

Battery powered vehicle and drive system

Abstract: An electrically driven vehicle, such as a local transportation vehicle, suburban runabout, light service vehicle or golf car, has a non-articulated frame with drive wheels associated with one end and a steerable wheel or wheels with the other end. Each of the drive wheels has its own permanent magnet direct current motor drive. The motors pass through a series-connected stage with unlimited differential action to a parallel-connected stage with limited differential action as the vehicle is brought up to speed from a stationary position. No mechanical differential is necessary and the vehicle may have a very low center of gravity and excellent center ground clearance. The drive system provides dynamic braking and energy restoration, with attendant control and energy saving advantages. This contributes to good traction and steerability under the varying operating conditions encountered. The weight of the batteries for the vehicle is sprung by the rear axle, so that the frame is relieved of carrying bending loads associated with the considerable proportion of total weight represented by the batteries. A vehicle embodying the invention can comfortably carry two 180-pound riders and two 20 or 30-pound golf bags more than 40 holes on a moderately hilly golf course using four standard 621/2 pound 6-volt rechargeable batteries, and this use can be repeated indefinitely, using two or more interchangeable battery packs. The vehicle can perform as well with four batteries as other currently manufactured vehicles do with six.

Aircraft towing braking system

Abstract: System for providing automatic synchronization of towing tug and aircraft braking systems during aircraft towing operations. A tow brake controller utilizing an aircraft brake pressure control circuit provides aircraft automatic brake pressure control signals in the aircraft automatic braking system in response to tractor braking signals. The brake pressure control circuit provides an increase and then a decrease in aircraft automatic braking system pressure in response to tow vehicle operator applied brake pressure.

Apparatus and method for reducing effective inductance in a dynamic braking circuit

Abstract: A method and apparatus are disclosed for reducing effective inductance and providing balanced line-to-line voltages in induction machine dynamic braking circuits which utilize braking resistors to substantially increase the full torque braking range of the machine. The current phase lag caused by the inductive property of conventional braking resistors, is substantially reduced by rectifying the current provided to the braking resistor through a three-phase rectifier bridge. This reduction of the current phase lag permits a reduction in the capacitance required to compensate for the effective inductance in the dynamic braking circuit. Furthermore, because the braking currents flow through a common braking resistor, the line-to-line stator motor voltages are inherently balanced. If the prior art braking impedance control is also employed, the rectifier bridge need carry current only if dynamic braking is required when motor voltage is greater than the maximum voltage of the inverter supplying the machine. Where the braking resistor may be varied in a step-wise manner, the amount of dynamic braking capacitance needed for inductive compensation is reduced below the substantial reduction realized for a non-variable resistor. Depending upon the required degree of performance and the allowable complexity of the braking circuit, the prior art braking impedance control may be eliminated and the effective impedance of the common braking resistor may be varied in either a continuous or a step-wise manner.

Braking mode control for a chopper controlled d-c electric motor

Abstract: A control system for effecting smooth braking resistor staging of a chopper controlled direct current electric motor. The control system utilizes auxiliary switches mechanically coupled to resistor by-pass contacts to sense actual motion of the by-pass contacts and to provide signals for reducing the chopper duty factor. In a preferred embodiment the chopper duty factor is reduced to an intermediate level between maximum and minimum duty factor by modification of an error signal representing the difference between actual motor current and commanded motor current so as to maintain the control system in a closed loop condition. In a further embodiment during dynamic braking the chopper duty factor is limited to a level sufficient to assure adequate operating voltage by checking for a minimum voltage level on a line filter capacitor, which capacitor supplies power for separate field excitation, whenever the chopper is at maximum duty factor and immediately reducing the duty factor if the capacitor voltage is less than the minimum voltage.

Method and device for regulating the braking cycle for an individual wheel on a vehicle

Abstract: A method and a device for regulating a vehicle wheel braking cycle. The braking pressure is caused to vary in response to control parameters, causing the wheel to decelerate and accelerate in an alternating fashion. During acceleration the value of acceleration is measured, and a signal representing the maximum acceleration is compared with a braking pressure signal for the purpose of determining the amount of pressure increase needed over the braking pressure used during the acceleration. The braking pressure is then increased to the value determined by the maximum wheel acceleration.

Braking system for vehicle axle

Abstract: A brake assembly is described in which two disk elements are mounted on a common axis of rotation so that a single braking unit can control braking action on both of the disk elements. The described arrangement provides for smaller diameter braking disks with no loss in braking effectivness of a given system.

Blending valve for electro-pneumatic brakes

Abstract: An electro-pneumatic brake valve includes counteracting torque motors which rotate a cam in response to friction brake pressure, dynamic braking effort and/or an electrical control signal. The cam actuates switching elements to apply or release the friction brakes via a pair of solenoid actuated valves which control fluid flow from the valve inlet to the friction brake actuators and from the friction brake actuators to vent.

A simplified, interactive simulation for predicting the braking and steering response of commercial vehicles

Abstract: An interactive computer program which predicts the response of trucks and tractor-trailers to braking and steering inputs is documented. The mathematical model simulating the vehicle and the input/output of the computer program have been designed to elicit simplicity of operation rather than extreme accuracy. Thus, quasi-static load transfer is used, and wheel spin degrees of freedom are neglected. Special features of the simulation include provisions for tandem axles with inter-axle load transfers, dual tires, brake imbalance, and the effectiveness of antilock braking systems. /Author/

Apparatus for safety braking of vehicles

Abstract: A method and an apparatus for performing said method, for the safety braking of automotive vehicles wherein a trailer is pulled by a prime mover, in such manner so as to eliminate the problems of jack-knifing and the like on sudden stops, and wherein a feature of the method and apparatus involves the dynamic augmentation of the braking torque of an over-driven motor, where the motor is connected to the trailer wheels and the friction brake is added to the negative torque of the over-driven motor in proportion to the negative torque generated by the over-driven motor during deceleration.

Transportation: Dynamic braking

Abstract: Points out that the kinetic energy of rapid transit trains that is normally dissipated as heat during braking can be converted to potential energy

The influence of tire properties on passenger vehicle handling. volume ii - technical report

Abstract: The overall objectives of this research program to identify the properties of tires that affect vehicle dynamic response and to evaluate the degree to which the various tire parameters enter into this response. The main elements of this research study involved: (1) a laboratory tire test program to measure the performance parameters of interest (braking and lateral force coefficients, aligning and overturning moments, etc.) on selected tires with specified construction properties, (2) a vehicle test program in which the effects of tires with different properties and parameters were measured on four cars using nine wet and dry test maneuvers, and (3) a fundamental vehicle simulation study designed to determine the effect of individual tire parameters on various vehicle performance metrics.

Deceleration control device in braking

Abstract: PURPOSE: To offer a deceleration control device in braking of high controlling accuracy by giving a direct constant deceleration command. COPYRIGHT: (C)1976,JPO&Japio

Control of the Saturistor Motor

Abstract: The performance of the saturistor motor is improved by the addition of capacitors in the secondary circuit. The ac performance on run-up is changed considerably with increased torque production,reduced supply current and a power factor nearer to unity. DC dynamic braking is also influenced to the extent of increased braking torque, and reduced run-down times under comparable braking conditions. Braking using capacitor excitation is shown to be improved by the presence of saturistors. Analysis of the various modes of operation is discussed with acceptable prediction of the experimental characteristics.