PhD project: Modelling, Testing and Analysis of a Regenerative Hydraulic Shock Absorber

System

Abstract: Recoverable energy in vehicle suspension systems has attracted intensive attention in

recent years for improved performances. Various design concepts and structures of regenerative

suspensions have been presented and investigated to recover the energy of linear motion and

vibration between the vehicle body and wheels which is from irregular road surfaces. Unfortunately,

the usability of the regenerative technologies in operating vehicle suspension systems is still

insufficient for providing detailed techniques to be productised to unleash its market potential.

To advance the technologies, a regenerative hydraulic shock absorber is investigated rigorously by

examining the system at various developing stages including fabricating a prototype of a commonly

used shock absorber, modelling all hydraulic, mechanical, electromagnetic processes, simulating its

behaviours, testing its desirable performance and evaluating its on-road usability, which has

resulted in a number of new understandings that brings forward considerable advancements on the

technologies improvements.

Based on the configuration of the prototype a comprehensive mathematical model is developed for

the regenerative hydraulic shock absorber system. The various losses and nonlinearity have been

taken into account in modelling hydraulic, mechanical, electromagnetic processes, which allows

more detailed influences and agreeable predictions with the experimental works to be obtained. The

introduction of the gas-charged hydraulic accumulator into the system been explored in both

modelling and testing to realise the smoothing effect in this work, and shown to be a useful means

by which the hydraulic behaviour and recoverable power can be improved with desirable damping

performance and acceptable recoverable power.

Model parameter identifications and refinements based on the online data are systemically

investigated. It has found that the pressures, rotation speeds and electrical outputs, which are readily

available in the system, are sufficient to determine and refine uncertain model parameters such as

the voltage constant coefficient, torque constant coefficient, generator internal resistance and

rotational friction torque using a common least square method.

The original experimental rig and measurement systems for the study of regenerative hydraulic

shock absorber are designed and built. The variations in motor pressure and shaft speed under

different excitations, and also voltage output and recoverable power at different electrical loads.

Additionally, the experimental works are not only used to validate the predicted results

comprehensively, but also to offer a practical evaluation method for the system at various operating

conditions. Additionally, control strategies and their realisation on a general propose PC computer

are developed based on constant voltage, current and resistance schemes to carry out the

investigation of the system performances, which allows it to be fully evaluated upon the

compromise between the damping behaviour and power regeneration performance for different road

conditions.

Furthermore, the simulation of the entire system and parameter computations are all realised on the

Matlab platform, which provides sufficient flexibility to take into account more influence factors for

accurate and detailed analysis and thus can be the effective mathematical tools for further

development researches in the directions such as the optimisation of the structures, control

strategies and system integrations.

Solidworks

Experimental rig design (Suspension/shock absorber system):

Details of Bearing housing design and assembly:

PARTS LIST DETAIL DESIGN OF BEARING HOUSING

Part

No. Quantity Description Remarks

B1 1 HOUSING

B2 1 OUTER BEARING FLANGE:DIA240 x

32 THK

B3 1 INNER BEARING FLANGE:DIA 240 x

32 THK

B4 1 MAIN SHAFT:80 DIA x 525 LG

B5 1 SPACER

B6 1 INNER BEARING:

DUAL ROW SPHERICAL ROLLER

ID 65, OD 140, W 48

SKF REF:22313E SKF 22313E

B7 1 OUTER BEARING:

DUAL ROW SPHERICAL ROLLER

ID 70, OD 150, W 51

SKF REF: 22314E SKF 22314E

B8 2 LIP SEAL C/W DUST LIP

ID 55, OD 75 W 8

SIMRITS BAUMSLX7: 55-75-8 BAUMSLX7:55-75-

8

PARTS LIST SADDLE ASSEMBLY

MATERIAL:SIMRIT 75KM 585

B9 2 O’RING

ID 160x3 CROSS SECTION O-ring 160-3

MATERIAL: SIMRIT 83FKM 592

B10 1 RETAINING PLATE: 460 x 80 x 25 BH 012

B12 1 LOCK NUT

1 M60 x 2 SKF KM12

B13 1 LOCKING WASHER M60 SKF MB12

B14 16 M12 x 40 LG, HEX HEAD M/C SCREW

B15 16 M12 SPRING WASHER

B16 2 M20 x 70 LG HEX HEAD M/C SCREW

B17 2 M20 SPRING WASHER

B18 2 M10 GREASE NIPPLE

B19 1 BED

B20 1 SADDLE ASSEMBLY

B21 1 KEY

Part

No. Quantity Description Remarks

S1 1 SADDLE TOP PART

S2 1 SADDLE RIGHT SUPPORT PART

S3 1 SADDLE LEFT SUPPORT PART

S4 14 M8 SPRING WASHER

S5 14 M8 x 40 LG, HEX HEAD M/C SCREW

S6 2 M20 x 38 LG, HEX HEAD M/C SCREW

S7 2 M20 SPRING WASHER

FEA analysis

Static structure design and shape optimisation

Diesel engine cylinder FE analysis

Simulink

Half car model (tractions, torques and various inputs)

All files available upon request, two examples have been show in the following.

Quarter car model (Suspension system with control methods)

7-DOF full-car model (Partial view)

Regenerative hydraulic shock absorber system (Partial view)

Data acquisition process

Designing and creating an engineering application with Lab-Windows/CVI starts with the user

interface, and an intuitive creation of graphical user interface (GUI) designer is built. The Lab-

Windows/CVI offers several key features, such as advanced debugging, automatic code generation,

data management and integrated source code control.

Measurement panel design

SERVOTEST Operation panel and process design input signals

Experimental rig of regenerative hydraulic shock absorber system

Measurement system design (transducers and power supplies)

Current and voltage transducers design