7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 1/8

SKF steering unitsCompact and robust

Maintenance-free

Plug-and-play

7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 2/8

By-wire technology offers several advantages

in the operation and control of industrial and

off-highway vehicles. When mechanical or 

hydraulic systems are replaced with by-wire-

technologies, for example, programmable

steering functions and ergonomic improve-

ments are possible. By-wire technology can

also improve vehicle efficiency and enhance

performance. Vehicles with better perform-

ance that consume less energy, can signifi-

cantly reduce cost of ownership for the enduser.

SKF was one of the first companies to

develop electronic steering units for industrial

vehicles. The first unit, based on proven sen-

sor bearing technology, is an excellent solu-

tion for applications such as fork lift trucks.

Requirements put on steering input devices

for industrial and off-highway vehicles vary.

For many applications a compact unit with

constant steering friction and moderate reso-

lution of the steering signals is appropriate.

Other applications may require more sophisti-

cated functions and performance such as

• steering feel dependent on operating

conditions

• tangible end stops

• programmability: for example the number 

of turns lock-to-lock can be set by the

vehicle manufacturer or vary depending on

operating parameters.

Therefore, SKF offers two different types of 

steering units. Both are safe and reliable,

maintenance-free and cost-effective plug-and-play solutions.

Steer-by-wire for modernoff-highway vehicles

SKF steering units

A compact and robust design

SKF steering units are designed to operate in

harsh environments. The housing, made of 

corrosion resistant steel or polyamide, fully

protects the inner mechatronic components.

The stub shaft for connecting the steering

wheel is made of stainless steel. The compact

flanged housing makes it easy to mount the

unit in any position.

7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 3/8

Possible applications

• Forklifts

• Harvesters

• Tractors

• Construction site equipment

• Electric vehicles

• Boats

Features

• Compact input device for steering

wheel position, steering speed and

direction

• Redundant steering signal output

• Steering feel constant or variable

• Non-contact sensors

Benefits

• Enables more ergonomic cabin design,

improved operator comfort and

increased productivity.

• Reduction in components enhances

system reliability.

• Redundant signals and robust design

provide an extra margin of safety.

• Integrated and maintenance-free

technology reduces lifetime cost.

A maintenance-free ”steeringcolumn”

SKF steering units replace conventional steer-

ing columns and eliminate the need for main-

tenance. The units contain sealed SKF Explor-

er bearings providing long service life and

reliable performance. These maintenance-

free steering units will never require adjust-ment or relubrication during their expected

service life.

Reliable control signals

Either non-contact incremental or absolute

position sensors are used to track the move-

ment of the steering wheel. These magnetic

sensors do not wear, are protected from

external influences, and are designed to pro-

vide maximum service life. As steering

requires a safety sensitive design, redundancy

of the output signals is necessary. SKF steer-ing units are made to support the safety

architecture of steer-by-wire systems.

A cost-effective solution

SKF steering units can simplify current

designs. They are easy to install, mainten-

ance-free and reliably fulfil the demands of 

industrial and off-highway vehicle by-wire

steering systems. When considered over the

entire product lifetime, these units are a very

cost-effective solution.

7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 4/8

AHE steering encoderunits – with constantsteering friction

SKF AHE steering encoder units consist of 

• a stainless steel stub shaft to mount thesteering wheel

• two non-contact rotary incremental or 

absolute position sensors

• a friction mechanism providing constant

steering feel

• a compact and robust housing

• an SKF rolling bearing

There are three basic versions of AHE steering

encoder units:

• Unit with incremental sensors for standard

resolution (max. 256 increments per turnof the steering wheel), designation

AHE-5400 A,

• Unit with incremental sensors for high

resolution (max. 1024 increments per turn

of the steering wheel), designation

AHE-5700 A,

• Unit with absolute sensors and analogue

output, designation AHE-5800 A.

AHE steering encoder units are available both

with flanged housing or without flange.

Table 1

Mechanical data

Weight 0,55 kg

Load carrying abilityof the steering column:

Bending moment, static 100 Nm

Axial force, static 2 kN push1 kN pull

Table

Ambient conditions

Operating temperature –40 to +85 °C(–40 to +185 °F)

7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 5/8

Table

Sensor data

Incremental sensor Incremental sensor Absolute positionwith standard resolution with high resolution sensor with high(AHE-500 A) (AHE-5700 A) resolution

(AHE-5800 A) Sensor type non-contact, non-contact, non-contact,

redundant Hall redundant Hall redundant Hallelements elements elements

 Power supply 5 to 12 V DC 5 to 12 V DC 5 to 12 V DC

(24 V DC on request) (24 V DC on request)

Resolution 64 impulses per 256 impulses per 12 bitsrevolution, a maximum revolution, a maximum (output 0 to 5 V DC)of 256 increments can of 1024 incrementsbe evaluated can be evaluated

Signal output Open-collector, Push-pull-output, Analoguesquare wave, square wave, with 0,5 to 4,5 V DC  with 90° phase 90° phase difference,

difference, incremental incremental

Fig. 1

AHE steering encoder unit with a flanged housing(main dimensions, mm)

22

25

94

65

250

65

35

37,2

5

7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 6/8

ADD steering units – withvariable steering feel

The ADD-7001 steering unit is an advanced

addition to the SKF steering unit range. It is

designed as a cost-effective, reliable, and

maintenance-free plug-and-play solution.

An ADD-7001 steering unit consists of:

• a stub shaft to mount the steering wheel

• two independent non-contact rotary

absolute position sensors

• two independent CAN interfaces

• an electro-magnetic brake

• a corrosion resistant steel housing

• SKF rolling bearings

The ADD-7001 steering unit detects the posi-

tion of the steering wheel and provides pro-

grammable steering feel and end stops.

Individual ”steering feel”

The integrated electro-magnetic brake pro-

vides the driver with realistic feedback by

changing the torque resistance to the steering

wheel. Feedback is controlled by the vehicle

controller via the CAN-bus or by the micro-

processor in the steering unit.

The brake is further used to simulate end-

stops that keep the steering wheel from turn-

ing when the actual end-stop position of the

steered wheels is reached. By a special

patented solution, the brake is released as

soon as the steering wheel is moved in the

opposite direction. The steering unit end-stop

positions are programmable, unlike mechan-

ical or hydraulic steering systems where the

end-stops are fixed. In addition, the steering

ratio can be programmed to vary with vehicle

speed or other operating parameters.

Standard interfaces withredundancy

Two non-contact absolute posit ion sensors

are integrated into the steering unit. Both

sensors and output channels comprising the

microprocessors and CAN-bus interfaces are

redundant. The primary unit provides the

angle of the steering wheel via the primary

CAN-bus circuit. It also controls steering feel

by varying the current to the electro-magnetic

brake. The secondary unit is a back-up for 

emergency control. The status of each sensor is monitored. In case of errors, they are auto-

matically reported to the vehicle controller via

the CAN-bus. Thus the unit is considered

fail-safe.

Suitable for various applications

The ADD-7001 steering unit is seen as an

input device for steer-by-wire systems in all

types of off-highway vehicles such as indus-

trial, agricultural and forestry vehicles, con-

struction equipment as well as in ships. The

unit can be integrated into either electro-

mechanical or electro-hydraulic steering sys-tems. It can eliminate the need for expensive

mechanical connections or hydraulic systems.

The ADD-7001 steering unit meets electro-

magnetic compatibility guidelines.

7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 7/8

Table

Mechanical data

Weight 2,3 kg

Load carrying abilityof the steering column 

Bending moment, static 200 NmAxial force, static 1 kN

Static steering moment 1 Nm

Max. brake moment(end stop) 10 Nm

Table 5

Electrical data

Supply voltage 12 V DC(24 V DC on request)

Wrong wiringprotection for all connectors

Sensor resolution 12 bit (0,09°)CAN-bus version 2.0B,

250 kbit/s max updaterate 5 ms, CAN trans-ceiver is ISO 11898-2compliant

Power-up time max. 1 s

Table

Ambient conditions

Operating temperature –40 to +85 °C(–40 to +185 °F)

Fig.

ADD-7001 steering unit(main dimensions, mm)

22

50

100

max. 168,5

70

52,5

7

7/15/2019 6271 EN

http://slidepdf.com/reader/full/6271-en 8/8

SKF is a registered trademark of the SKF Group.

© SKF Group 2007The contents of this publication are the copyright of thepublisher and may not be reproduced (even extracts)unless permission is granted. Every care has been takento ensure the accuracy of the information contained in thispublication but no liability can be accepted for any loss or damage whether direct, indirect or consequential arisingout of the use of the information contained herein.

Publication 71 EN · June 2007

Printed in Sweden on environmentally friendly paper. skf.com