Hydropneumatic Suspension Systems

Preface
Contents
1 Suspension Systems Basics
	1.1 Requirements for Suspension Systems
		1.1.1 Minimize Accelerations on the Isolated Side
		1.1.2 Equalize Variations of Vertical Wheel Forces
	1.2 Suspension Technology Basics
		1.2.1 General Setup of a Suspension System
		1.2.2 General Behavior of a Suspension System
		1.2.3 Alteration of Suspension Parameters
	1.3 Hydropneumatic Suspension Compared to Other Suspension Methods
		1.3.1 Comparison of Spring Characteristics
		1.3.2 Comparison of Damping Characteristics
		1.3.3 Level Control
		1.3.4 Non-functional Requirements
	1.4 Applications for Hydropneumatic Suspension Systems
2 Spring and Damping Characteristics of Hydropneumatic Suspension Systems
	2.1 General Setup and Working Principle
	2.2 Spring Characteristics
		2.2.1 Thermodynamic Background
		2.2.2 Calculation Predeterminations
		2.2.3 Non Preloaded Hydropneumatic Suspension Systems
		2.2.4 Systems with Mechanical Preload
		2.2.5 Systems with Constant Hydraulic Preload
		2.2.6 Systems with Variable Hydraulic Preload
	2.3 Damping Characteristics
		2.3.1 Boundary Friction Damping
		2.3.2 Fluid Friction Damping
		2.3.3 End-of-Stroke Damping
	2.4 Combined Operation of Spring and Damper
3 Dimensioning of the Hydropneumatic Suspension Hardware
	3.1 Dimensioning of the Hydraulic Spring Components
		3.1.1 Cylinder
		3.1.2 Accumulator Gas Precharge
		3.1.3 Detailed Calculation of p0 and V0
	3.2 Dimensioning of the Hydraulic Damping Elements
		3.2.1 Single-Acting Cylinder in a System Without Hydraulic Preload
		3.2.2 Double-Acting Cylinder in a System Without Hydraulic Preload
		3.2.3 Double-Acting Cylinder in a System with Hydraulic Preload
		3.2.4 End-of-Stroke Damping
4 Hydraulic Components Design
	4.1 Cylinders
		4.1.1 Function and Requirements
		4.1.2 Types of Cylinders
		4.1.3 Sealing Elements
		4.1.4 End-of-Stroke Damping
		4.1.5 Types of Support Elements
	4.2 Accumulators
		4.2.1 Function and Requirements
		4.2.2 Types of Accumulators
		4.2.3 Methods to Reduce Diffusion Pressure Loss
		4.2.4 Usage of Pressure Relief Valves
		4.2.5 Integration into Available Design Space
	4.3 Flow Resistors
		4.3.1 Non Adjustable Orifices and Throttles
		4.3.2 Flow Direction Depending Resistors
		4.3.3 Adjustable Flow Resistors
	4.4 Hydraulic Lines and Fittings
		4.4.1 Function and Requirements
		4.4.2 Required Flow Cross Section
		4.4.3 Tubes
		4.4.4 Hoses
		4.4.5 Fittings
	4.5 Control Manifolds
		4.5.1 Functions and Requirements
		4.5.2 Block Design
5 Level Control
	5.1 Self-Pumping Suspension Elements
	5.2 Mechanical Level Control with External Hydraulic Power Supply
	5.3 Electronic Level Control with External Hydraulic Power Supply
		5.3.1 Function
		5.3.2 Hydraulic Circuits Using On/Off-Valves
		5.3.3 Hydraulic Circuits Using Proportional Valves
		5.3.4 Control Algorithms
	5.4 Electronic Level Control with Dedicated Power Supply
6 Special Functions of Hydropneumatic Suspension Systems
	6.1 Suspension Lockout
		6.1.1 Lockout by Blocking the Hydraulic Circuit
		6.1.2 Lockout at the Compression End Stop
		6.1.3 “Quasi-lockout” Through High Spring Stiffness
	6.2 Adjustment of the Zero Position
	6.3 Alteration of Roll and Pitch Behavior
		6.3.1 Coupling Cylinders on Corresponding Sides
		6.3.2 Decoupling Cylinders
		6.3.3 Coupling Double-Action Cylinders on Opposite Sides
	6.4 Spring Rate Adjustment by Selective Connection of Accumulators
	6.5 Tire-to-Ground Force Optimization in All-Wheel Suspension Systems
7 Suspension Testing
	7.1 Goals of Suspension Testing
		7.1.1 Functional Testing
		7.1.2 Durability Testing
	7.2 Test Scenarios and Methods
	7.3 Measurements, Evaluation and Optimization
		7.3.1 Pressure
		7.3.2 Position/Displacement
		7.3.3 Acceleration
		7.3.4 Online Versus Offline Evaluation
	7.4 Typical Project Testing Steps
		7.4.1 Initial Function Testing/Analysis
		7.4.2 Hardware-In-The-Loop (HIL) Testing
		7.4.3 Laboratory Functional Testing
		7.4.4 Machine Functional Testing
		7.4.5 Durability Testing
8 Design Examples
	8.1 Tractor Front Axle Suspension TLS by John Deere
	8.2 Passenger Car Axle Suspension by Citroen
	8.3 Suspension Projects—Lessons Learned
9 Important Patents
	9.1 Improvement of Suspension Characteristics
		9.1.1 DE1755095
		9.1.2 DE19719076
		9.1.3 DE10107631
		9.1.4 DE10337600
		9.1.5 DE4221126
		9.1.6 DE4234217
		9.1.7 US9039021
		9.1.8 DE4223783
		9.1.9 US6167701
		9.1.10 DE19949152
		9.1.11 US6398227
		9.1.12 DE102008012704
	9.2 Roll Stabilization and Slope Compensation
		9.2.1 GB890089
		9.2.2 DE3427508
		9.2.3 DE10112082
		9.2.4 US4411447
		9.2.5 US6923453
	9.3 Suspension Lockout
		9.3.1 US3953040
		9.3.2 DE4308460
		9.3.3 DE4032893
10 Looking into the Future
	10.1 Components
	10.2 Systems
	10.3 Energy Consumption
	10.4 Trend Towards Electronics
Index of Symbols and Abbreviations
Dimensions and Dimension Related Parameters
Forces and Force Related Parameters
Accumulator Related Parameters and Pressures
Parameters Defining the Dynamic Suspension Behavior
Miscellaneous Parameters
General Use of Indices
References
Index