Mechatronics, Electrical Power, and Vehicular Technology 05 (2014) 83-90 

 

Mechatronics, Electrical Power, and 

Vehicular Technology 
 

e-ISSN: 2088-6985 

p-ISSN: 2087-3379 

Accreditation Number: 432/Akred-LIPI/P2MI-LIPI/04/2012 

 

 

www.mevjournal.com 
 

© 2014 RCEPM - LIPI All rights reserved 

doi: 10.14203/j.mev.2014.v5.83-90 

EVALUATION OF POTENTIAL USAGE OF INCREMENTAL-TYPE 

ROTARY ENCODER APPLICATION FOR ANGLE SENSING  

IN STEERING SYSTEM  
 

Sunarto Kaleg
 a,

*, Aam Muharam 
a
, Muhammad Redho Kurnia 

a
, Abdul Hapid 

a
 

a
Research Centre for Electrical Power and Mechatronics, Indonesian Institute of Sciences 

Komplek LIPI, Building 10, Basement, Jl. Cisitu No. 154D, Bandung, West Java, 40135 Indonesia 

 
Received 30 October 2013; received in revised form 7 November 2014; accepted 10 November 2014 

Published online 24 December 2014 

 

Abstract 
The main target of a steering system is that the driver can change vehicle trajectory in accordance with the desired direction. 

Power steering has become a standard feature in automobile. It provides assisting power when the driver turns the steering wheel. 

The well-known power steering types include; Hydraulic Power Steering (HPS), Electro - Hydraulic Power Steering (EHPS), and 

Electric Power Steering (EPS). EHPS or EPS uses an Electronic Control Unit (ECU), which is specific for each vehicle. The 

ECU should be able to regulate power of electric motor to provide corresponding assisting power for the steering wheel. 
Therefore, ECU requires input signals, one of which is vehicle wheel angle that can be indicated from the vehicle steering wheel 

angle. Incremental type of Rotary Encoder (RE) is used in steering angle sensor on a minibus. RE specification used was 60 

pulses per rotation and the minibus steering transmission specification is 3.5 round of right wheel off angle to the left whe el off 

angle. So we get the RE angular resolution of 6º per pulse and 105 number of pulses to half of the steering transmission ratio. 
Repeatability then was tested against a steering angle counter module. Testing was done with a test cycle consisting 3 repetitions: 

condition center of the steering wheel, the steering wheel is turned to full right, then to the full left, then back to the right up to 

the steering wheel center. The results obtained were 2 pulses deviation, or equivalent to 12º of steering angle. 

 
Keywords: vehicle steering system, rotary encoder, incremental, steering wheel angle, repeatability. 

 

I. INTRODUCTION 
Most of the vehicles that roam the city road 

are comprised of piloted vehicles such as cars, 

buses, and trucks. The trajectory is a tri-

dimensional or planar curve, determined by a 

guidance system controlled by a human pilot. 

The guidance system acts by exerting forces on 

the vehicle that are able to change its trajectory 

[1].  

Steering system is constituted of several main 

components as described in Figure 1: steering 

wheel, steering column, and steering transmission 

[2]. The steering wheel must be designed such it 

can be easily controlled and allows firm grip. It is 

made from composite and plastic enabling 

comfort and firm grip. The power which 

generated by the steering wheel is distributed to 

the steering transmission component through the 

steering column. The column is precisely and 

several segments built such that its axis is not in 

line with that of the steering transmission. The 

segments also contribute to the ergonomic 

steering wheel positioning. Steering transmission 

amplifies the power applied by the driver which 

will be transmitted to the vehicle’s wheels. 

The effect of the reduction gear varies with 

vehicle type. Suppose a sedan utilizes a steering 

system that exhibits steering transmission ratio of 

16. This configuration should enable curving the 

car wheels angle of 40° for 1.7 rotations relative 

to the steering wheel center. 

Two types of steering transmission are 

commonly used; rack-pinion type and screw-

sector or re-circulating ball bearing type. The 

first type, as seen in Figure 2, is commonly used 

by passenger car or small cargo vehicle [2]. Its 

versatility is mainly contributed by its simple 

mechanism, and favorable mechanical efficiency 

due to relatively low gear friction [1]. The 

direction of the forces acting on the steering 

transmission is parallel to lateral axis relative to 

the vehicle. This force causes the driver-

controlled wheel to have the same lateral forces 

acting on it as it was on the rest of the wheels. In * Corresponding Author: Tel: +6222.2503055 
E-mail: sunarto.kaleg@lipi.go.id 

http://dx.doi.org/10.14203/j.mev.2014.v5.83-90


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84 

return, the driver’s ability to react to different 

kinds of road condition greatly enhanced. 

Figure 3 shows the screw and sector type of 

steering transmission [3]. This type commonly 

used in middle class vehicle up to heavy cargo 

due to its compact transmission design that 

allows spacious engine room. It is quite 

beneficial compared to the previous type which 

forces the transmission to be placed right at the 

wheel axis. This type of transmission is 

composed of screw shaft that acts as the 

trajectory of the ball bearing causing minimal 

friction which in return greatly increases the 

mechanical transmission efficiency. Despite these 

benefits, the driver may not be able to react 

accordingly as well as if the previous type was 

used. It is caused by the inability of the wheels to 

transfer the lateral force to the driver-controlled 

wheel. Steering torque originated from the driver-

controlled wheel itself. However, the torque from 

the wheels cannot return to the driver-controlled 

wheel. 

Power steering has become a standard feature 

in automotive. It provides assisting power when 

the driver turns the steering wheel. The well-

known power steering types include; Hydraulic 

Power Steering (HPS), Electro - Hydraulic Power 

Steering (EHPS), and Electric Power Steering 

(EPS). EHPS or EPS uses an Electronic Control 

Unit (ECU), which is specific for each vehicle.  

Nowadays, HPS is commonly used in most 

vehicles. The energy source is originated from 

the hydraulic energy which is produced by the 

engine turned the fluid pump. Excessive power of 

the engine enables HPS to be able to be used 

properly in many situations. The fluid pump 

components and its tank is shown in Figure 4. 

HPS was deeply researched due to the 

increasing needs on high fuel efficiency, and 

strict gas emission standard. At low engine 

rotation, the power produced by HPS is very low 

causing the steering wheel to be heavy when 

rotated especially for large curving angle. On the 

other hand, when the engine spins at high angular 

velocity, the necessary power needed to supply 

the fluid pump increases while the power needed 

to turn the steer decreases. Hence, marking the 

flaw of HPS which lies in energy efficiency [4]. 

In response to this matter, EHPS was developed. 

It enables controlled and adjustable fluid pump 

mechanism relative to the vehicle speed and 

condition. Its main component is electric motor 

 

Figure 1. Steering system scheme on the main components that constitute it [2] 

 

Figure 2. Rack and pinion-type steering transmission [2] 

 

Figure 3. Screw and sector-type steering transmission [3] 



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85 

which is used to supply the fluid pump. The 

electronic control unit (ECU) controls the electric 

motor. The EHPS scheme is depicted in Figure 4. 

Figure 4 also illustrates the ECU component 

which is integrated with the fluid pump [5]. The 

compact design enables the installation to be both 

flexible and integrated with steering 

transmission. Finally, the fluid used in either 

EHPS or HPS is the same thus allowing it to be 

used in all types of vehicles. 

In EPS, an electric motor can be directly 

connected either to the axis of steering 

transmission or to the steering column. Figure 5 

shows a column-type EPS [6]. It is noticeable 

that EPS is more compact than both HPS and 

EHPS. Furthermore, by utilizing a proper ECU, 

an EPS can produce the same power that is on 

par with both HPS and EHPS. Both EHPS and 

EPS use ECU which is specific for each types of 

vehicle. In order to acquire suitable additional 

power, the ECU should be able to regulate the 

power produced by the electric motor. Several 

factors are used as inputs for ECU including 

torque of the steering wheel, vehicle speed, 

angular speed of steering wheel, and wheels’ 

angle [1]. The ECU in the EPS also uses the 

electric motor current as feedback signals to 

produce appropriate assisting power. However, 

when the power steering fails, such a steering 

system must allow a driver to take over manually. 

EPS can independently design treatments of, 

for example, road surface information and 

disturbance information and steering safety and 

also can obtain safe, comfortable steering 

performance which is easily tunable has been 

proposed [7]. In line with Intelligent Transport 

System (ITS) trend, in the future, automatic 

controlled steering is predicted to be 

implemented [8-10]. 

Nowadays, absolute-type optical sensor, such 

as rotary encoder (RE), is commonly used. 

Absolute-type RE has an advantage in terms of 

the generated digital data that is ready to be 

processed. Methode Electronics released steering 

sensor which utilizes this type of sensor which 

has 1080° resolution [11]. Moreover, its 

sensitivity is about 1.5°, and has been equipped 

with a computer that is able to detect both 

steering angle and steering rotation speed. As 

shown in Figure 6, the light will go through 

combination of codes producing light patterns 

which will be sensed by the photocells. It will 

then be processed by the microprocessor whose 

result will be given to the ECU to regulate the 

response of electric motor according to the angle 

measurement.  

Disadvantages of absolute-type RE are it 

requires many photocells to be mounted and 

alignmented very precisely [12]. Other 

disadvantage is that the disk made with unequal 

 
1. Steering column assembly 

2. Steering column with intermediate spindle 

3. Rack and pinion steering with external drive 

Figure 5. Illustration on column-type EPS [6] 

 

Figure 4. The scheme of electro-hydraulic power steering 

(EHPS) [5] 



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86 

spaced slots, make it expensive to be produced. 

The incremental-type RE has only one disk of 

equally spaced slots. Wheels’ angle is determined 

by counting the number of slots that pass the 

photocells. This type RE only use two photocells 

for counting and convey the disk direction. So, it 

makes incremental-type RE cheaper than the 

absolute-type RE. This paper reports experiment 

results of angle sensor using incremental-type RE 

to investigate its possibility to be used as a 

steering angle sensor. 

 

II. INCREMENTAL-TYPE ROTARY 
ENCODER AS ANGLE SENSOR  

Autonics E80H is a hollow shaped 

incremental-type RE. This design, as shown in 

Figure 7, aims to connect to steering column 

without any transmission medium such as gear or 

pulley. The output is frequency of two waves, A 

and B, and one reference wave named Z. The 

shape of the superposition of the two waves is 

quadrature as shown in Figure 8 [13]. 

Pulse counter and direction determination are 

essential for RE to be able to be used as a 

steering angle sensor. As seen in Figure 9, 

direction can be determined by using two unique 

conditions of wave A relative to wave B. 

Suppose; an incremental-type RE has two waves 

namely A and B or V1 and V2. Hence, when V2 

is low while V1 remains high, the direction is 

counter-clockwise. On the other hand, when both 

V1 and V2 are low, the direction is clockwise. 

The obtained direction can be combined with V2 

through AND gate to count the pulse. The pulse 

increases when the RE axis is rotated clockwise, 

and decreases when rotated counter-clockwise 

[12]. The pulses counter flowchart is shown in 

the Figure 10, which is processed using 

microcontroller. Steering shaft position is 

counted from CW (count of pulse A in form of 

clockwise) and reduced by CCW (count of pulse 

A in form of counter-clockwise), then multiplied 

with RE resolution used.  

 

III. ACCURACY AND REPEATABILITY 
RE was characterized by its resolution rather 

by its calculation accuracy. It is able to accurately 

detect motion while limited by the quality of the 

rotation [14]. Suppose that an element deflection 

due to loading produces thread toleration of 0.1 

inches. By using RE whose resolution is about 

1,000 pulse per rotation, a reading of 0.001 

inches can be read. However, it will never be able 

to read a movement of about 0.1 inches.  

The accuracy of an RE in steering system is 

determined by the precise reading of the pulse 

against the curving angle. The accuracy 

limitation of the steering system is affected by 

 

Figure 7. Incremental-type RE E80H released by  

Autonics [13] 

 

Figure 6. Steering sensor made by Methode Electronics [11] 

 

Figure 8. The output of the wave A, B, and Z [13] 
 



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tolerance value of the steering angle due to 

tolerances on mechanical components 

connections steering column, steering 

transmission and ball joint tolerance at the end of 

steering transmission with kingpins. 

Repeatability is an RE ability to show the 

same value when rotated from the reference point 

to some point, and then back to the same 

reference point. In terms of steering system, the 

reference point is the center of the steer, and the 

wheels are positioned parallel to each other; 

enabling the vehicle to move in straight path. If 

rotated clockwise and counter-clockwise, then 

two curves in first quadrant and third quadrants 

will be obtained respectively. Figure 11 

illustrates two curves in the first quadrant and 

third quadrant forming straight line bridging both 

quadrants. If the reference point is in the origin of 

the coordinate system (0, 0), then it is obvious 

that the ordinate will be negative to the left of the 

curve, and positive to the right of the curve. 

Repeatability is affected by the pulse deviation 

which is typically occurs in optical RE. This 

deviation is formulated as follows, 

                                 
                                     
                   (1) 

Instrument error is an eccentric code, wrong 

pattern, worn-out bearing, and optics flaws. 

Quadrature error is a combined effect of wave 

toleration, duty-cycle, and other variables in 

basic analog signals. Interpolation error is an 

error that occurs when the RE resolution raises 

after four calculations per optics cycle. Suppose, 

RE with resolution of 512 pulses per rotation was 

used for angle sensing. Then, the angle resolution 

would be 0.703125° per pulse. The computer will 

interpolate this value until the allowed rounding 

point which causes pulse increment. Quantization 

error is an error that is not originated form RE 

but will always occur in digital instrumentation 

[15]. Suppose we have digital number whose 

value is between 1 and 0, then this number must 

be quantized to either 1 or 0. 

IV. RESULT ON INCREMENTAL-TYPE 
RE 

This type of RE was used in the construction 

of steering sensor of a passenger car. The 

resolution of the RE is 60 pulses per rotation 

while the specification of the steering 

transmission is 3.5 rotations relative from the 

 

Figure 10. The flowchart process counting of steering shaft 
position 

 

 

Figure 9. Direction determination through V1 and V2 processing [3] 



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fixed angle of the right to the fixed angle of the 

left. The resolution of the RE angle is formulated 

as follows, 

                 
    

                             
 (2) 

Using equation (2), if specification of RE is 

60 pulses per rotation, then the RE angle 

resolution is 6
o
 per pulse. If the center of the 

steering wheel (the wheel facing straight 

forward) is half of the steering transmission ratio 

which is 1.75, then the number of pulses from the 

center of the steering wheel to the fixed angle of 

the wheels can be calculated using the formula, 

                                
                            (3) 

The generated pulse is 105 relative from the 

center of the steering wheel to the fixed axis of 

the wheels. One cycle of tests comprised of 3 

repeats; from the center of steering wheel, it was 

turned to the all the way right, and the all the way 

to the left and then back to the initial position. 

Figure 12 shows the number of pulses within one 

cycle. The value is negative when the steer was 

turned left and positive when turned right. Data 

sampling was taken in every 30 degree of 

steering wheel angle. Then resulting total 133 

data in one cycle. Count 5 pulse in every data 

theoretically. 

From the tests, the relation between pulse 

deviation and number of tests was obtained as 

depicted in Figure 12. Figure 12 shows us that 

the highest pulse deviation is 2 pulses. The pulse 

 
Figure 11. Relation between steering angle and number of pulses 

 

 
Figure 12. Generated pulses versus pulse deviation within one cycle 



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deviation occurs in random data. It occurs when 

the encoder stops in the transition position i.e. 

position that does not generate one count. Then it 

one count is added to next data. Next, if the 

encoder stops in perfect position, there is no 

pulse deviation. The pulse deviation value can be 

converted to the actual angle deviation using the 

formula, 

 
                                 
                  (4) 

The angle deviation that occurred was 12°.  

Figure 13 shows the value of steering angle 

tolerance is 5 degree. The angle deviation 

resulted by pulse deviation larger than permitted 

steering angle tolerance. These values will be 

used for developing methods to resolving RE 

signal conditioning, less pulse deviation, 

resulting less angle deviation. However, an RE 

which exhibits a much higher resolution to 

produce much smaller angle deviation produced, 

so that smaller angle deviation is can be used. 

 

V. CONCLUSION 
EHPS and EPS are additional power system 

for the steering wheel which uses specific ECU 

for each vehicle types. Power regulation of the 

electric motor is necessary to acquire the suitable 

additional power. One of the ECU inputs is the 

wheel’s angle which can be sensed using optical 

sensor such as rotary encoder (RE). Among the 

types of RE, incremental type whose resolution is 

about 60 pulses per rotation was used. After 

repeatability tests, which comprised of 3 repeats; 

from the center of steering wheel, it was turned to 

the all the way right, and the all the way to the 

left and then back to the initial position. It 

produced pulse deviation of 2 pulses which 

equals to 12° of angle deviation. The angle 

deviation resulted by pulse deviation larger than 

permitted steering angle tolerance. These values 

will be used for developing methods to resolve 

RE signal conditioning, less pulse deviation, 

resulting less angle deviation. 

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corner/tech-info/suspension-

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Figure 13. Toyota minibus steering angle tolerance measurement 



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[12] C. T. Killian, Modern control technology: 

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