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Vehicle System Dynamics: InternationalJournal of Vehicle Mechanics andMobilityPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/nvsd20

Design of a hydraulic anti-lockbraking modulator and an intelligentbrake pressure controller for a lightmotorcycleC-Y Lu & M-C Shiha Department of Mechanical Engineering , National Cheng-KungUniversity , Tainan, Taiwan, ROCPublished online: 06 Aug 2006.

To cite this article: C-Y Lu & M-C Shih (2005) Design of a hydraulic anti-lock braking modulatorand an intelligent brake pressure controller for a light motorcycle, Vehicle System Dynamics:International Journal of Vehicle Mechanics and Mobility, 43:3, 217-232

To link to this article: http://dx.doi.org/10.1080/00423110412331282878

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Design of a hydraulic anti-lock braking modulator and an

intelligent brake pressure controller for a light motorcycle

C.-Y. LU and M.-C. SHIH*

Department of Mechanical Engineering, National Cheng-Kung University, Tainan, Taiwan,ROC

The object of this paper is to design a new hydraulic modulator and an intelligent sliding modepulse width modulation (PWM) brake pressure controller for an anti-lock braking system, forapplication to light motorcycles. The paper presents a design principle and a mathematicalanalysis of the hydraulic anti-lock braking modulator. The intelligent sliding mode PWMbrake pressure controller based on vehicle acceleration is designed and tested. A three-phasepavement experiment and a rear brake influence test are undertaken to verify the performanceof the controller and the modulator. A light motorcycle is built for the real vehicle anti-lockbraking experiments. The experimental results show that both the intelligent controller and thehydraulic modulator designed in the study perform well in the anti-lock braking operation.

1. Introduction

In the past few decades, many types of anti-lock braking systems (ABS) have beeninstalled in different kinds of vehicle [1 – 11], but not in lightweight motorcycles. Lightmotorcycles, for example a 125cc scooter with a 100 – 130 kg dry weight, are usedfrequently in big cities. When riders of motorcycles without ABS perform emergencybraking maneuvers, they are frequently thrown from the vehicle. This is particularlyapparent in wet conditions. As a result, non-ABS light motorcycles cause manycasualties. Most of the ABS installed on four-wheel vehicles adopt an additionalhydraulic pump and valves to regulate the brake pressure. But both size and costconstraints prevent their installation on light motorcycles. In this study, a hydraulicanti-lock braking modulator is designed and tested for light motorcycle ABS.

The relationship between the longitudinal tyre frictional coefficient, the lateral tyrefrictional coefficient and the slip ratio, all of which play an important role in ABSdesign, are described [12 – 17]. As the slip ratio increases from zero, the longitudinaltyre frictional coefficient typically reaches a maximum and subsequently approaches a

*Corresponding author. Email: mcshih@mail.ncku.edu.tw

Vehicle System DynamicsVol. 43, No. 3, March 2005, 217 – 232

Vehicle System DynamicsISSN 0042-3114 print/ISSN 1744-5159 online ª 2005 Taylor & Francis Group Ltd

http://www.tandf.co.uk/journalsDOI: 10.1080/00423110412331282878

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horizontal asymptote. Stopping distance can be shortened effectively if the slip ratio iskept between 8% and 30% [12]. At the same time, there is also good steeringcontrollability. For different road surfaces, the characteristics between the tyrefrictional coefficient and slip ratio can be described by a semi-empirical tyre model [18].Significant system parameters such as vehicle mass and environmental influences (rain,snow, etc.) all combine to exacerbate this control problem.Recently, the VSS (variable-structure system) design technique has been successfully

applied to ABS control problems [19, 20]. These two papers present sliding mode ABScontroller design, using pulse width modulation (PWM) and switching control, andboth obtain good experimental results on their test stand. Furthermore, a brakepressure control logic using sliding mode PWM controller has been considered by Wu[21]. Five preset values of angular acceleration of wheel instead of the slip ratio decidethe control logic of his controller. The accurate slip ratio is not easy to ascertainbecause the equipment required to measure the actual vehicle velocity is expensive. Inthis study, an intelligent anti-lock brake pressure control logic, which uses the vehicleacceleration as the main input is designed and tested.

2. System description

2.1 Experimental light motorcycle

Two rotary encoders are installed on the front and the rear wheel, respectively, tomeasure the angular velocity. An accelerometer located at the center-of-gravityposition of the test motorcycle is used to measure the acceleration while braking. Twopressure transmitters are installed on the brake pump and the brake calipers,respectively, of the front wheel brake. A microcomputer is used to record datameasured by the sensors and control an electric motor through an AD/DA card. Thevehicle velocity is calculated by integration of the measured acceleration. Two worntyres with average groove depths of 1.8 mm and inflation pressure of 2.2 bar are usedfor the experimental light motorcycle.

2.2 Hydraulic anti-lock braking modulator

An electric motor is adopted for its smooth mechanical behaviour to drive a screw inthe hydraulic anti-lock braking modulator designed in the study. The hydraulicdiagram of the anti-lock braking modulator is shown in figure 1.

2.2.1 Brake handle. Figure 2 shows a rider gripping a brake handle with a force Fp.Force Fp and Fout is acted on the brake handle with an equation of leverage:

Fout

Fp¼ la

lb¼ lab

_Fp ¼ � 1

tpFp þ 1

tpK

ð1Þ

_F out ¼ � 1

tpFout þ lab

tpK ð2Þ

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where K is a steady value of the gripping force and tp is a time constant while thegripping force is gradually acted.

2.2.2 Brake pump. From Newton’s second law, a dynamic equation of the brake pump(see figure 3) can be derived:

Fout � AmDPm � Cm _xm ¼ Mm€xm; DPm ¼ Pm � P0 ð3Þ

where xm is the displacement of the spool in the brake pump, Mm is the mass of thespool in the brake pump, Pm is the pressure in the brake pump, P0 is the ambientpressure, Cm is the damping ratio in the brake pump, and Am is the cross-section areaof the spool in the brake pump. Therefore,

€xm ¼ Fout � AmPm � Cm _xmMm

ð4Þ

When the brake fluid flows from the brake pump to the modulator, the volume flowrate, Qm, is:

Figure 1. Hydraulic diagram of the anti-lock braking modulator designed in the study.

Figure 2. Free-body diagram of brake handle.

Design of brake systems for a light motorcycle 219

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Qm ¼ CdA5

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2

rðPm � PLÞ

sð5Þ

The derivative of the volume in the brake pump, _Vm, is:

_Vm ¼ Am _xm �Qm ¼ Am _xm � CdA5

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2

rðPm � PLÞ

s: ð6Þ

Therefore, the derivative of the pressure in the brake pump is:

_Pm ¼ b_Vm

Vm0¼ b

Vm0½Am _xm � CdA5

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2

rðPm � PLÞ

s� ð7Þ

where r is the density of brake fluid, bis the bulk modulus, Cd is the dischargecoefficient, A5 is the area of the throttle in the brake pump, PL is the pressure in the leftchamber in the modulator, Vm0 is the initial volume of Vm.

2.2.3 Modulator. The scheme of the modulator is shown in figure 1.

2.2.3.1 Operating sequence. As shown in figure 1, when a motorcycle rider grips thebrake handle, the brake fluid will flow from the brake pump to the brake disc throughthe modulator. When the wheel is locked, the control device will send commands to theelectric motor to drive the screw descendent, and the flow passage in the modulator willbe closed concurrently. At the same time, the volume of the right chamber will beincreased to decrease the brake pressure. When the wheel is released, the control devicewill send commands to drive the screw ascendent and decrease the volume of the rightchamber to increase the brake pressure. When the rider loosens his grips, the brakefluid flows from the brake calipers to the brake pump rapidly through a reflux checkvalve in the modulator before the flow passage is opened by the electric motor. But theflow passage of the modulator may not be opened by a breakdown of the electric motorafter a long operating period. In this case, the brake fluid can flow from the brakepump to the brake calipers through a safety check valve in the modulator; therefore theoriginal brake ability is still kept when the electric motor is at fault.

2.2.3.2 Mathematical analyses of the hydraulic modulator. The flow passage is openinitially. As shown in figure 1, the volume flow rate from the brake pump to the left

Figure 3. Free-body diagram of brake pump.

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chamber is shown in equation (5). The volume flow rate from the left chamber to theright chamber is:

Qc ¼Cd � Ac �

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2ðPL�PRÞ

r

qifPL4PR and the flow passage is open

Cd � Ac �ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2ðPR�PLÞ

r

qif PR4PL and the flow passage is open

0 when the flow passage is closed

8>><>>: ð8Þ

The volume flow rate from the right chamber to the brake disc is:

Qd ¼CdAd

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2ðPR�PSÞ

r

qif PR4PS

�GdAd

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2ðPS�PRÞ

r

qif PS4PR

:

8<: ð9Þ

The volume flow rate from the right chamber to the left chamber through the refluxcheck valve is:

Qb ¼ Cd � Ab �ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2�ðPR�PLÞ

r

q; if PR4PL

0 ; if PL4PR

:

(ð10Þ

The volume flow rate from the left chamber to the right chamber through the safetycheck valve is:

Qs ¼ Cd � As �ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2�ðPL�PRÞ

r

q; if PL � PR4KP

0 ; if PL � PR5KP

:

(ð11Þ

The volume flow rate caused by the displacement of the modulating shaft in themodulator is:

Qh ¼ Ah � _h : ð12Þ

where Ac is the cross-section area of the flow passage in the modulator, Ad is thecross-section area of the flow passage between the left chamber and the brake disc,Ab is the cross-section area of the reflux check valve, As is the cross-section area ofthe safety check valve, KP is a preset pressure to open the safety check valve, Ah isthe cross-section area of the modulating shaft, h is the displacement of themodulating shaft.

The derivative of the pressure in the left chamber is shown in equation (13). Thederivative of the pressure in the right chamber is shown in equation (14).

_PL ¼ bQm �Qc þQb �Qs

VL0: ð13Þ

_PR ¼ bQc �Qd þQs �Qb �Qh

VR0: ð14Þ

Where, VL0 is the initial volume of brake fluid in the left chamber, VR0 is the initialvolume of brake fluid in the left chamber.

Design of brake systems for a light motorcycle 221

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2.2.4 Brake calipers. The derivative of the pressure in the brake calipers is shown inequation (15). The relationship between the brake pressure and the brake torque isshown in equation (16).

_PS ¼ bQd

VS0ð15Þ

Tb

PS¼ Kb ð16Þ

where VS0 is the initial volume of the brake fluid, Tb is the brake torque, PS is thepressure in the brake disc, Kb is a torque gain.

2.3 Characteristic of the hydraulic anti-lock braking modulator

The characteristic data of the hydraulic anti-lock braking modulator designed in thestudy depends on its geometric dimensions. The modulator is driven by an electricmotor, as shown in figure 1. One may increase the maximum pressure rate byincreasing the area of the modulating shaft, Ah, or raising the screw pitch. Butoppositely, the torque requirement of the electric motor will be increased, too. Themaximum pressure change is proportional to the displacement of the modulating shaft,h, but a higher displacement of the shaft will make a longer modulator, which maycause trouble in installing the modulator on a light motorcycle. These properties haveto be traded off for applying the modulator in different kinds of vehicle. In the presentstudy, the maximum pressure rate and the maximum pressure change are set to be 150bar/sec and 100 bar, respectively. The response time of the system is mainly related tothe response of the electric motor, 1.5 ms.

3. Intelligent sliding mode PWM brake pressure controller design

3.1 Sliding mode PWM controller

In the study, sliding mode control theory is adopted to design the controllers because ofits robustness [19]. A sliding mode PWM slip-ratio controller has been designed andtested [22]. In the study, the sliding mode PWM controller is designed to trace a targetbrake pressure determined by an intelligent brake pressure control logic described insection 3.3, and the sliding mode index Sslide is defined as:

Sslide ¼ Eslide þ l � _Eslide ð17Þ

where Eslide=Pref – Ps; Pref is the target brake pressure and l is a strictly positiveconstant. _Eslideis the derivative of Eslide:

_Eslide ¼ dEslide

dt� Eslideðkþ 1Þ � EslideðkÞ

Tsð18Þ

where TS is the sampling period.

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3.2 Brake pressure control logic on ABS

Wu [21] developed a brake pressure control logic for ABS on his passenger car ABStest stand in 2001. The target brake pressure of this control logic is not determineddirectly. There are five fixed preset values of the angular acceleration of wheel in thiscontrol logic, as shown in figure 4. From the comparison of the angular accelerationand the five values, the brake pressure control logic could determine a target brakepressure to increase, hold or decrease the brake pressure. Nevertheless, the five presetvalues must be different while braking on different kinds of road surface. But the wayto identify those five values on different kinds of road surfaces is not illustrated in hisstudy. Furthermore, the tyre conditions are changed after a long operating period, andthe five preset values do not fit their conditions at all times.

3.3 Intelligent brake pressure control logic

A scheme of the intelligent brake pressure control logic designed in the study for ABS isshown in figure 5. Figure 6 shows a block diagram of the intelligent anti-lock brakingcontrol system. In the study, a target brake pressure is determined directly by thevehicle acceleration and vehicle velocity. A fuzzy regulator is employed to compensateinfluences on the anti-lock braking control system. The main equation of the intelligentbrake pressure control logic is shown below:

Pref ¼ Pint þ a1 � aþ a2 � Vv ð19Þ

where a1 and a2 are two parameters of the target brake pressure, and Pref. A is thevehicle acceleration. Vv is the vehicle velocity. Pint is a compensated value determinedby the fuzzy regulator.

Because of the feedback of the vehicle acceleration, the changes of the roadconditions or the tyre conditions could be identified through the intelligent brakepressure control logic designed in the study. If the brake pressure is too high, the tyrewill be locked too soon, and in addition, the tyre frictional force will decrease [12].Therefore, the target brake pressure will decrease with decreasing vehicle deceleration.When the vehicle is braking from a high frictional pavement to a low one, the vehicledeceleration and the target brake pressure will be decreased at the same time by theintelligent brake pressure control logic to avoid the wheels locking.

When a vehicle is running on a dry pavement, the tyre frictional force is larger than itis when running on a wet pavement. The road conditions change the tyre frictionalforce. The tyre frictional force is also changed with tyre lifetime. The properties of aused tyre are not the same as a new one. Those changes are difficult to be considered inan anti-lock braking controller, and an accurate and complete tyre model is not easy toidentify. But the change of vehicle acceleration due to the change of the tyre frictionalforce is easy to measure. The intelligent brake pressure control logic is based on thevehicle acceleration.

There are a number of influences that lead to measurement errors of the vehicleacceleration, such as vehicle pitch due to the suspension system, tyre flexibility,inclination of the road, vibrations in heavy braking conditions, etc. But thecomponents of those influences in the vehicle brake direction are relatively small tothe vehicle deceleration, except the inclination of the road. If the motorcycle is runningon an inclined road surface, the measurement of the vehicle acceleration will be

Design of brake systems for a light motorcycle 223

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influenced by the component of the gravity. At that time, the fuzzy regulator willmodify the influence to the target brake pressure. The fuzzy regulator designed for theintelligent brake pressure control logic in the study is shown in figure 7, whichdetermines the value of Pint. The purpose of the fuzzy regulator is to modify the targetbrake pressure to a more accurate value. Da and DPs are the input signals of the fuzzyregulator, where, Da= a(k) – a(k – 1), DPs=Ps(k) –Ps(k – 1). No matter what theinclination of the road surface (uphill or downhill), if Da is not increased or decreasedwith DPs, the fuzzy regulator will determine a compensated value, Pint, to decrease orincrease the target brake pressure, Pref. Inclined roads only influence the target brakepressure at the beginning of braking, and the fuzzy regulator will modify it as the timesof sampling increase. But if the inclined angle of road is too big or the inclination anglevaries with time, the brake performance may be worsened, and a level meter will needto be installed. Through the same rules of the fuzzy regulator, other influences will onlybring a small vibration to the target brake pressure as shown in experiments in thestudy, but not worsen the performance of the controller.The value of a1 could be determined directly by the proportion of the brake pressure

and the vehicle acceleration. The maximum value of the tyre friction coefficient versusslip ratio curve changes with vehicle velocity [22]. A small increase of the target brake

Figure 4. Brake pressure control logic [21].

Figure 5. The scheme of the intelligent brake pressure control logic.

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pressure while the vehicle velocity is decreasing is considered in the study, a2. Theestimation of a1 and a2 does not and cannot be accurate. The accurate values of a1 anda2 are time-variant, because the tyre conditions or the brake conditions are notconstant. The estimation errors of a1 and a2 will be compensated by the fuzzy regulatorthrough the same rule between Da and DPs described in the previous paragraph.

The input signals, which are crisp values but nonfuzzy variables, of the fuzzyregulator must be fuzzified by the fuzzifier. The fuzzifier performs a mapping from thecrisp point to a fuzzy set. A fuzzy set is denoted by a linguistic term such as ‘positiveerror’, or ‘negative error’, and is characterized by membership functions. The fuzzifierof the fuzzy regulator is a nonsingleton (triangular) fuzzifier. The fuzzy rule base of thefuzzy regulator is IF-THEN rules, which is typically expressed in the form of a fuzzyconditional statement:

Ri: IFDa is Ai ANDDPs is Bi, THEN Pint is Ci

where Ai, Bi and Ci are fuzzy sets characterized by membership functions mA(Da),mB(DPS) and mC(Pint), respectively. If there are n fuzzy sets for each of the variables Da,

Figure 7. The fuzzy regulator.

Design of brake systems for a light motorcycle 225

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DPs, Pint, then there will be n2 total number of fuzzy rules. This fuzzy rule set could becombined into one single rule by the following operator: R=R1[R2[. . .[Rn

2.To compute the subsequent output Pint, a max –min inference method, is used to be

the fuzzy inference engine in the paper and shown below:

mGðPintÞ ¼ maxfmin½mAiðDaÞ; mBi

ðDPsÞ; mRiðDa;DPs;PintÞ�g ð20Þ

After applying the max –min inference technique, the subsequent output is obtained.However, this output value is still a fuzzy quantity. The output of a fuzzy logiccontroller generated by the fuzzy algorithm must be defuzzified to a crisp value by thedefuzzifier. The center-of-gravity method is preferred to be the defuzzifier, which isrepresented by

Pint ¼Pn2i¼1

Pint;i � mGðPint;iÞPn2i¼1

mGðPint;iÞð21Þ

The value of the Pint is obtained. The membership functions used in the fuzzy regulatorare shown in figure 8 and the fuzzy rule base is shown in figure 9.

4. Experimental results

All the experiments are operated for a 10 ms sampling period and the brake handle isgripped at around 45 km/hr. All the experiments are taken on a dry low frictionalpavement [22]. As shown in figure 10, brakes are applied to both the front and the rearwheels at the beginning of the test with a set of a1 (7 4.05) and a2 (7 0.12). Table 1shows the stopping distance of the 50 times experimental results.

4.1 Three-phase pavement test

When a brake test is considered on a three-phase pavement with the initial vehiclevelocity at around 45 km/hr, a longer brake time is required to show the performanceof the intelligent controller apparently. Instead of increasing the initial vehicle velocity,for the sake of safety, only braking the front wheel is adopted to increase the braketime in this test.

Figure 8. The membership functions.

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Figure 9. Fuzzy rule base.

Figure 10. One of the experimental results using intelligent sliding mode PWM brake pressure controller witha moderate initial braking pressure.

Design of brake systems for a light motorcycle 227

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The three-phase road surface is composed of the following conditions: (i) the road isdry for an initial 5.5 m distance, (ii) the road is wet between 5.5 and 10 m and (iii) theroad reverts back to dry again beyond 10 m distance.Figure 11 shows the experimental results using the intelligent sliding mode PWM

brake pressure controller on the three-phase pavement to trace the target brakepressure with another set of a1 (7 4.82) and a2 (7 0.12). There is apparentlychattering in the target brake pressure of the experimental results. This phenomenonis caused by the inconsistent property of the road surface and the influencesdescribed in section 3.3. The intelligent brake pressure control logic detects thechanges of the road condition accurately and the brake is indeed controlled aroundthe target brake pressure by the sliding mode PWM controller. Table 2 shows thestopping distances of the 50 experimental results at the three-phase pavementtest.

4.2 Rear brake influence test

The rear brake system of the light motorcycle in the study is not a hydraulic type; it is amechanical drum. Most of the rear brakes on light motorcycles are drum systems. Onecannot use a hydraulic ABS to control a mechanical drum brake system. This kind ofbrake will be a problem to hydraulic anti-lock braking control. The mechanical drumbrake system can be considered as another influence to the intelligent brake pressurecontrol logic. Although the brake force is not constant during the whole brake process,the variation of it is small, except when the wheel is locked. An undisputable fact is thata hydraulic ABS can do nothing for a locked mechanical drum brake system. When therear drum wheel of the light motorcycle is not locked, the variation of vehicleacceleration caused by the change of rear brake force or other influences will becompensated by the fuzzy regulator of the intelligent controller with the same rulesdescribed in section 3.3.To show the influence of the rear drum brake system, a rear brake influence test is

mapped out in this section. The front wheel is braked at the beginning of the test tillthe end and the rear wheel is braked with a moderate force at around 7.5 m after thetest is begun. As shown in figure 12, the target brake pressure is increased with theincreasing vehicle deceleration caused by the brake of the rear wheel and thendecreased by the modification of the fuzzy regulator. The influence caused by theaction of rear brake system with a non-locked rear wheel is controllable. The changesof brake condition are detected by the intelligent brake pressure control logic welland the performance of the controller is not worsened in the rear brake influence test.Table 3 shows the stopping distances of the 50 experimental results at the rear brakeinfluence test.

Table 1. The stopping distances of the 50 times experimental result (both wheels are braked at the beginning)using intelligent sliding mode PWM brake pressure controller.

Stopping distances Times

9.6 – 9.8 m 419.8 – 10 m 9

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Figure 11. One of the experimental results using intelligent sliding mode PWM brake pressure controller onthe three-phase pavement with a moderate initial braking pressure.

Design of brake systems for a light motorcycle 229

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Table 2. The stopping distances of the 50 times experimental result at the three-phase pavement test usingintelligent sliding mode PWM brake pressure controller.

Stopping distances Times

14.4 – 14.6 m 1814.6 – 14.8 m 3114.8 – 15.0 m 1

Figure 12. One of the experimental results of the rear brake influence test.

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4.3 Comparison

To show the performance of the intelligent sliding mode PWM brake pressurecontroller, comparisons with the other kinds of controller are given in this section. Thebrake handle is gripped at around 45 km/hr. The P –R conditions presented by Gunturand Ouwerkerk [23] and the sliding mode PWM slip-ratio controller [22] are adopted inthe comparison. Only the front wheel is braked in the comparison brake test. Detailedexperimental data about brake times and stopping distances are shown in table 4. Oneof these is arbitrarily chosen and compared with each other. The performances of theintelligent sliding mode PWM brake pressure controller are not apparent on the dry,low frictional pavement. As shown in table 4, when the road conditions (three-phasepavement test) or the brake conditions (rear brake influence test) are changed, theperformances of the intelligent sliding mode PWM brake pressure controller are betterthan the other kinds of controller.

5. Conclusions

1. The experimental results show that the design of the hydraulic anti-lock brakingmodulator is applicable for the light motorcycle.

Table 3. The stopping distances of the 50 times experimental result at the rear brake influence test usingintelligent sliding mode PWM brake pressure controller.

Stopping distances Times

10.2 – 10.6 m 3810.6 – 11.0 m 12

Table 4. The results of different kinds of controller with moderate initial braking pressure.

Controller type Test conditions Brake times (s) Stopping distances (m)

Without ABS Dry low frictionalpavement

2.09 13.11

Three-phase pavementtest

2.51 15.69

Rear brake influence test 1.88 11.75P1R4 Dry low frictional

pavement1.95 12.19

Three-phase pavementtest

2.45 15.31

Rear brake influence test 1.84 11.5Sliding mode PWMslip-ratio controller

Dry low frictionalpavement

1.86 11.63

Three-phase pavementtest

2.38 14.88

Rear brake influence test 1.77 11.06Intelligent sliding modePWM brake pressurecontroller

Dry low frictionalpavement

1.84 11.54

Three-phase pavementtest

2.25 14.60

Rear brake influence test 1.69 10.54

Design of brake systems for a light motorcycle 231

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2. Through the three-phase pavement test, the changes of road conditions could bedetermined accurately through the intelligent brake pressure control logicdesigned in the study. The brake pressure could be controlled around the targetvalues well by the sliding mode controller.

3. Many influences are considered in the study. The influence of the rear drumbrake system of the light motorcycle is considered in the rear brake influence testand modified through the intelligent brake pressure control logic and the fuzzyregulator.

4. The performances of the system control are verified through the experiments ofthe three-phase pavement test and the rear brake influence test in the study.

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