Balanced brake control system

A balanced brake control system is provided for use in aircraft. An embodiment of the invention is presented for an aircraft having struts with both inboard and outboard braked wheels on the struts. In the detailed embodiment, an equalizer circuit is interposed between right and left brake pedals on an input side thereof and right and left inboard and outboard brakes on an output side thereof. This equalizer circuit ensures a first equal application of brake pressure to the right inboard and outboard brakes and a second equal application of brake pressure to the left inboard and outboard brakes, dependent upon pilot control of brake pedals. The first and second equal applications of brake pressure may differ to accommodate differential braking.

TECHNICAL FIELD

The invention herein relates to brake control systems for vehicles and, more particularly, to brake control systems for aircraft. More specifically, the invention is directed to a balanced brake control system ensuring uniformity of brake application between inboard and outboard brakes on a strut.

BACKGROUND OF THE INVENTION

Aircraft are often configured with multiple wheels on a strut, each having associated brakes. In the context of the discussion herein, inboard wheels and brakes on a strut are those closest to the main axis of the aircraft fuselage, while outboard wheels and brakes on a strut are those most distant from such axis.

In some aircraft, it has been noted that during certain braking activities, one set of brakes, typically the inboard or outboard brakes do virtually all of the braking, while a remaining set, such as the outboard or inboard brakes have little or no pressure applied above that necessary for lining contact. As a consequence of the disparity of braking activity on the struts themselves, uneven braking activity may result, particularly at low pedal application. Moreover, since the wear of carbon brakes is aggravated in low torque situations, a disparity between brake wear rates on a single strut or aircraft may result, giving rise to service complications and efficiency losses.

There is a need in the art for a balanced brake control system that ensures uniform application of brake pressure and resulting brake activity on the various wheels of a strut, ensuring uniform brake control and wear, without sacrificing maneuverability.

DISCLOSURE OF INVENTION

In light of the foregoing, it is a first aspect of the invention to provide a balanced brake control system for an aircraft in which uniform braking activity is ensured for each of the braked wheels on a strut.

Another aspect of the invention is the provision of a balanced brake control system for an aircraft in which uniform braking activity between sets of wheels, such as the inboard and outboard wheels on a strut is achieved, without interference with aircraft maneuverability.

Still a further aspect of the invention is the provision of a balanced brake control system for an aircraft in which sets of braking systems, such as the inboard and outboard braking systems of the aircraft are cross coupled, forcing the inboard and outboard brakes on a strut to react similarly during braking applications.

Yet a further aspect of the invention is the provision of a balanced brake control system for an aircraft in which differential braking remains possible, while ensuring equal brake application to the brakes of wheels of a common strut.

Another aspect of the invention is the provision of a balanced brake control system for an aircraft in which data of the braked wheels of an aircraft is shared among those braked wheels to ensure uniform braking application while accommodating differential braking control.

The foregoing and other aspects of the invention that will become apparent as the detailed description proceeds are achieved by a balanced brake control system for an aircraft, comprising: a right brake pedal producing a right brake command signal; a left brake pedal producing a left brake command signal; a first brake and a second brake comprising a first set of brakes; a third brake and a fourth brake comprising a second set of brakes; and an equalizer circuit interposed between said right and left brake pedals on an input side thereof, and said first and second sets of brakes on an output side thereof, said equalizer circuit ensuring a first equal application of brake pressure to a first subset of brakes taken from said first and second sets of brakes and a second equal application of brake pressure to a second different subset of brakes taken from said first and second sets of brakes.

Other aspects of the invention that will become apparent herein are achieved by a balanced brake control system for an aircraft, comprising: a right brake pedal producing a right brake command signal; a left brake pedal producing a left brake command signal; a plurality of right and left inboard brakes; a plurality of right and left outboard brakes; and an equalizer circuit interposed between said right and left brake pedals on an input side thereof, and said pluralities of right and left inboard and outboard brakes on an output side thereof, said equalizer circuit ensuring a first equal application of brake pressure to said plurality of right inboard and outboard brakes and a second equal application of brake pressure to said plurality of left inboard and outboard brakes.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings and more particularlyFIG. 1, it can be seen that a deceleration feedback control system for aircraft brakes is designated generally by the numeral10. It will be appreciated that the concept of the invention is presented herein in the context of an aircraft deceleration control system, but the invention is equally applicable to slip, torque, or various other types of brake control systems. Only for purposes of presentation is the invention configured in the context of a deceleration control system. Additionally, the embodiment described is adapted for an aircraft with two struts, each having a pair of wheels, but the concept of the invention extends to the sharing and utilization of data among any number of braked wheels to ensure uniform braking activity, while accommodating differential braking control. Yet further, examples of the invention are presented herein with regard to the balancing and uniformity of braking effort between inboard and outboard brakes, but the concept of the invention extends to achieving such balancing and uniformity between sets of brakes at any of various locations on an aircraft, such as sets of fore and aft, left and right, inner and outer, and the like.

The control system10is divided into an inboard system12associated with the brakes of the inboard wheels on the struts of the aircraft, and an outboard system14associated with the brakes of the outboard wheels on such struts. Of course, and as presented above, the control system10might be otherwise divided in keeping with the concept of the invention.

In somewhat standard fashion, a right brake control pedal16and left brake control pedal18are provided to allow pilot control of the braking torque, slip or deceleration by means of the presentation of a brake command signal. The outputs of the pedals16,18are provided as inputs to max filter/comparator circuits20,22, allowing as an output the maximum brake command signal from the right and left pedals16,18. This maximum signal is passed through scaling and filtering circuits24,26, the outputs of which are introduced to the positive input of summers28,30, as shown. Accordingly, the positive inputs of the summers28,30receive as a reference a signal corresponding to the greater of the decelerations requested by the pedals16,18. The negative inputs to the summers28,30are the outputs of differentiators/filters32,34. The differentiator/filter32receives as an input wheel speed signals corresponding to the instantaneous wheel speed of the right and left inboard wheels on the struts of the aircraft. Similarly, the differentiator/filter34receives as inputs the instantaneous wheel speed signals of the right and left outboard wheels of the struts. By differentiating and filtering the signals, the circuits32,34emit output signals corresponding to instantaneous aircraft deceleration as determined by inboard wheel speeds (circuit32) and outboard wheel speeds (circuit34).

The outputs of the summers28,30are respectively fed to deceleration feedback control circuits36,38which, as well known in the art, comprise proportional-integral-derivative control circuits that generate as outputs thereof control signals corresponding to a required brake pressure to achieve a desired rate of deceleration as dictated by the pedals16,18. A pair of max filters/comparators40,42receive the outputs of the deceleration feedback control circuits36,38and present as outputs the maximum value of the inputs. Accordingly, the outputs of the max filters/comparators40,42are the same, the output from the circuit40serving the inboard system12and the output of the circuit42serving the outboard system14. Accordingly, a deceleration control reference signal, and hence the brake pressure demand signal, are the same for both the inboard system12and the outboard system14.

It will be appreciated that the max filters/comparators40,42comprise an equalizer circuit44that cross couples the outputs of the deceleration feedback control circuits36,38to force the brake control reference signal, and hence the brake pressure demand signal, for both the inboard and outboard systems to be the same. As shown inFIG. 1, these identical signals are applied to a right inboard brake pressure control circuit46, left inboard brake pressure control circuit48, right outboard brake pressure control circuit50and left outboard brake pressure control circuit52. These circuits46,48,50,52receive brake command signals from associated brake pedals16,18augmented by the output of the equalizer circuit44as by the summer circuits54,56,58,60.

As shown, the positive input of each of the summer circuits54,56,58,60is a respective brake command signal from the associated pedals16,18. The negative input of each of the summer circuits54,60is the output of equalizer circuit44, which is a brake control reference signal. Accordingly, the output of each of the summer circuits54,56,58,60is a brake command signal of an associated pedal augmented by the output of the equalizer circuit44, ensuring the capability of differential braking as between struts. In other words, the brakes on the left side of the aircraft may have a different forceful application than those on the right, to accommodate steering, maneuvering and the like.

The outputs of summer circuits54,56,58,60are respectively applied to the positive inputs of summer circuits62,64,66,68. The negative input to these summer circuits is a pressure feedback signal of an associated brake, taken from an appropriate pressure transducer associated with the brake. Accordingly, the outputs of the summer circuits62,64,66,68are brake pressure demand signals applied to each of compensation circuits70,72.74,76which generate brake pressure control signals that are scaled for application to associated brake valves78,80,82,84, each having an associated valve driver. These brake valves control the application and release of brake pressure to associated brake assemblies86,88,90,92of associated wheels.

The balanced brake control system ofFIG. 1, with the implementation of the equalizer circuit44, ensures that the right inboard brake86and right outboard brake90receive the same brake pressure control signal at the respectively associated valves78,82. Similarly, the left inboard brake assembly88and left outboard brake assembly92receive the same brake pressure control signal at the associated valves80,84. Thus, inboard and outboard brakes on a common strut receive the same brake force application, while different struts are still capable of exercising different braking activity to accommodate differential braking as desired for steering, maneuverability and the like.

With reference now toFIG. 2, it can be seen that a second embodiment of the invention is designated generally by the numeral110. Again, the invention is shown in the context of a deceleration feedback control system for aircraft brakes, but the concept of the invention is again equally applicable to aircraft braking based on slip, torque, or other type signals. It will also be noted that the system110is substantially identical to the system10ofFIG. 1, accounting for the use of the same reference numerals, indexed by the number100. In the embodiment ofFIG. 2, the equalizer circuit144a, consisting of max filters/comparators140a,142a, is positioned upstream of its location in the system10ofFIG. 1. The equalizer circuit144areceives and operates upon cross coupled outputs of differentiators/filters132,134, the outputs of which correspond to calculated instantaneous aircraft deceleration. In the embodiment ofFIG. 2, the outputs of the differentiators/filters132,134are provided to the max filters/comparators140a,142a, such that the negative inputs to the summers128,130are the same value and represent the instantaneous aircraft deceleration rather than the deceleration feedback control signals as inFIG. 1. All other functions and operations of the circuit110are substantially the same as apparent from the description of the circuit10presented above. The primary difference between the embodiments ofFIGS. 1 and 2is the placement of the equalizer circuit, and the signals upon which it operates.

It will be appreciated by those skilled in the art that the invention described and presented herein may be in any number of configurations and implementations beyond the embodiments ofFIGS. 1 and 2. Any of various types of control signals, and control circuitry may be employed to assure brake equalization among any number of wheels, while allowing for differential braking as discussed above.

Thus it can be seen that the aspects of the invention have been satisfied by the structures and techniques presented above. While in accordance with the patent statutes only the best known and preferred embodiments of the invention have been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the scope and breadth of the invention reference should be made to the following claims.