System prevents tire skid during panic stops. Two mutually dependent accelerometers directly control solenoid valve which regulates braking pressure

Barthlome, D. E.

English

NASA Technical Reports Server

4 October 1975	 B75-10264 
NASA TECH BRIEF 
Langley Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Braking Action of Wheeled Vehicles Is 
Controlled Automatically During Minimum-Distance Stops 
.
An automatic system for controlling the braking 
action of wheeled vehicles prevents tire skid during 
panic stops. In this system, two mutually dependent 
accelerometers directly control a solenoid valve which 
regulates the braking pressure and automatically 
selects a pressure to produce a near-maximum 
braking effort and then maintains that pressure, 
essentially constant, throughout the remainder of the 
stop. In this manner, during minimum-distance 
stops, the maximum degree of wheel slip allowed by 
the system will be directly proportional to the degree 
of deceleration the vehicle is able to attain on a given 
road surface. The system not only eliminates the 
problem of skidding but also has the potential for 
automatically adjusting to changing braking con-
ditions so as to maximize tire traction on any road 
surface. 
The control system consists of a wheel sensor unit 
mounted on the rear axle of the vehicle and a brake 
pressure stabilization valve in the brake line leading to 
the rear wheels. The wheel sensor unit contains a 
rotational sensing mass, four rotational sensing-mass 
support springs, and a sensing-mass support plate 
which all rotate with the rear wheels. The sensor unit 
also contains a translational sensing mass, four 
translational sensing-mass support springs, and a 
sensing-mass support plate which are secured to the 
body of the vehicle. The rotating and nonrotating 
sensing masses are separated by ball bearings. 
Wheel and vehicle decelerations, which occur when 
the brakes are applied, produce inertial loads which 
act on the translational sensing mass as well as the 
rotational sensing mass and cause the sensing masses 
to press against one another. When the magnitude of 
the rotational load exceeds the magnitude of the 
translationai load, the rotational mass overpowers the 
translational mass and results in a clockwise rotation 
of the rotational sensing mass, relative to the wheels,
and a corresponding straightening of the support 
springs. At the same time, the translational sensing 
mass is forced rearward, with a corresponding 
increase in the deflection of the support springs, to 
activate a reed switch which, in turn, energizes the 
pressure stabilization valve. The sequence of events, 
from the instant the sensor unit begins its response 
until the pressure in the brake line has actually been 
stabilized by the valve, occurs in a time span as short 
as 15 milliseconds. 
When the brakes are applied, fluid flows from the 
master cylinder into the valve and forces the valve 
plunger off the valve seat; fluid then flows out to the 
wheel brake cylinders. When the brake lining contacts 
the brakedrums, pressure equalizes throughout the 
brake system and permits the valve plunger, by virtue 
of its weight, to settle back on the valve seat. With the 
valve plunger in this position and the reed switch in 
the sensor unit closed, the time required to stabilize 
brake pressure to the rear wheels is, essentially, the 
time required to energize the solenoid coil which 
presses the valve plunger firmly against the valve seat. 
Any one of the following operating modes can be 
obtained, provided the weights of the two sensing 
masses are properly proportional relative to one 
another. 
a. For maximum sensitivity, the rotational sensing 
mass is made sufficiently large, compared to the 
translational sensing mass, so that the unit will 
activate at virtually the instant the brake lining 
contacts the brakedrums. 
b. For minimal sensitivity, the rotational sensing 
mass is made sufficiently small, compared to the 
translational mass, so that the unit will not acti-
vate even to the point of locking the wheels. 
c. For optimum operating mode, located somewhere 
between the two extremes, the sensing masses are 
sized relative to one another so the system will 
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United Stales 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19750000264 2020-03-19T20:14:40+00:00Z
• permit the wheels to be decelerated to some rate 
just prior to wheel locking. At essentially the same 
instant that rate is attained, brake pressure will be 
stabilized by the system. 
The response of the wheel sensor is based not upon 
a single deceleration but upon the ratio of two 
decelerations, the wheels and the vehicle. As long as 
braking is normal, a stabilization of vehicular 
deceleration will be accompanied by a corresponding 
stabilization of wheel slip. During abnormal braking, 
vehicular deceleration will again stabilize at some 
maximum value while wheel slip will continue to 
increase. It is at that instant that this control system 
stabilizes brake pressure to the wheels thereby 
demonstrating its ability to maximize braking action 
on all operating surfaces.
Notes: 
1. The following documentation may be obtained 
from: 
North Carolina Science & Technology 
Research Center 
Post Office Box 12235 
Research Triangle Park, North Carolina 27709 
Single document price $3.25 
Reference: NASA TM X-72665, A Unique 
Concept for Automatically Controlling the 
Braking Action of Wheeled Vehicles During 
Minimum Distance Stops 
Technical questions may be directed to:

Technology Utilization Officer 
Langley Research Center 
Mail Stop 139-A 
Hampton, Virginia 23665 
Reference: B75-10264 
Patent status: 
This is the invention of a NASA employee, and U.S. 
Patent No. 3,744,850 has been issued to him. 
Inquiries concerning license for its commercial 
development may be addressed to the inventor: 
Mr. Donald E. Barthiome 
Mail Stop 315 
Langley Research Center 
Hampton, Virginia 23665 
Source: Donald E. Barthlome 
(LAR-11897)
. 
Categories: 06 (Mechanics) 
03 (Physical Sciences) 
B75-10264
	 05 (Life Sciences)	
.


Braking action of wheeled vehicles is controlled automatically during minimum-distance stops

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