• Home
  • Brakes
  • Chassis
  • DriveTrain
  • Exhaust
  • Tire
  • Video
  • Podcasts
  • News
  • Webinars
  • Magazine Archive
  • Advertise
  • Subscribe
  • Contact Us
Brake & Front End Babcox
Brake & Front End Babcox
Active Suspension Systems: Diagnosing Electronic Shocks And Struts

by Andrew Markel

Air Ride Diagnostics: It’s Not Just Swapping Parts

by Andrew Markel

Sponsored Content
A guide to replacing a wheel hub flange and bearing

by SKF

Arnott Introduces New Premium Air Suspension Strut For 2006-2011 Mercedes-Benz ML-Class

by Brake and Front End Staff

Consulting On Coilover Conversions

by Brendan Baker

10 Alignment Tips To Help You See Past The Angles

by Andrew Markel

Air Ride Diagnostics: Dodge Ram 1500

by Andrew Markel

Torque-To-Yield Suspension Components

by Doug Kaufman

Hyundai Tech Tip: Rear Brake Squeak On Application

by Brake and Front End Staff

Ride Height And Spring Diagnostics: Why Do Springs Droop?

by Andrew Markel

VIDEO: How Do Suspension Components Stay Together?

by Andrew Markel

Suspension/electronic suspension
May 15, 2017 10:48 am

Active Shocks And Struts

Share Tweet
Print Print Email Email
Andrew Markel

Andrew Markel,Director of Content, Brake & Front End Magazine

View bio

  • Bio
  • Recent Posts
  • Popular Posts

Andrew Markel is the editor of Brake & Front End magazine. He has been with Babcox Media for 15 years. He is a technician and former service writer and holds several automotive certifications from ASE and ­aftermarket manufacturers. He can be reached at [email protected]

VIDEO: Ford F-150 Electric Power Steering Rack Replacement

VIDEO: Rear Rotor Parking Brake Service

Undercar Overhaul Tips

TPMS Curve Balls

Nivomat Shocks: Mechanical Load Leveling

No More Toe And Go

VIDEO: Rear Rotor Parking Brake Service

VIDEO: Ford F-150 Electric Power Steering Rack Replacement

Undercar Overhaul Tips

Nivomat Shocks: Mechanical Load Leveling

active shocks struts abs stability bodySo, what makes a shock or strut “active?” For a shock or strut to be active, it must be able to react to three critical streams of information. First, it must act on information from the ABS and stability control system. Second, it must measure body movement. Third, it must detect the extent and rate of suspension movement. With these three pieces of information, the suspension can actively adjust the compression and rebound of the shock or strut.

Why would an engineer or automaker include this feature on a vehicle? An active dampener allows for a ride without compromise. The three inputs can be used to detect a rough road or an emergency situation where body roll could change the stability of the vehicle.

Electronic Shocks/Struts

Electronically adjustable shocks and struts use conventional mono-tube and twin-tube oil-filled dampeners. The rods, gas chambers and piston have the construction of passive units. Like a passive unit, they can fail if they leak, the gas escapes or the rods are bent. They can also wear out like a conventional unit as the oil inside breaks down and surfaces in the bore wear.

What makes these units unique are the valves with their variable orifices. These valves regulate the flow between the chambers on either side of the piston. The piston in some units, however, does not have any valving.

The size of the orifices controlled by electromagnetic solenoids that can control the valves very quickly. The electrical connections and solenoids are typically found outside the body and act on the valves inside the unit using magnetism. The signal to the solenoid is pulse-width modulated and varies the voltage to change the size of the orifice.

The valves and solenoids can’t be serviced or separated from the shock or strut. If a problem is detected with the system, the valves go into a fail-safe position that is fixed, and the system becomes passive. The driver is then alerted to the problem with a message or light on the instrument cluster or message center.

Most systems will perform a circuit check when the system wakes up. This typically involves sending a signal to fully open and close the valve. If the system detects an open, short or a voltage outside of the specifications, it will set a code.

active-struts-shocks-wheel-movement

Measuring Wheel Movement

Ride-height sensors not only measure the position of the suspension, but also the rate of movement. They are supplied with a voltage of around 5 volts. The signal voltage is changed as a magnet moves past a coil. Most sensors have three wires — ground, power and signal.

Internally, it is difficult to damage one of these sensors. Externally, however, the linkage that connects the sensor to the suspension arm can be damaged. Additionally, the connector can be damaged and cause a short or open that sets a code. If one of these sensors is replaced, it must be calibrated after it is installed.

Ride-height sensors are sometimes called suspension-position or wheel-displacement sensors. The data from the sensor is used to measure the movement of the suspension. By knowing how far and fast the suspension is moving, the module can use the information to determine the size of the orifice in the dampener to control compression and rebound. These sensors should be calibrated if a sensor is replaced, a module is reprogrammed or if the battery dies.

Measuring Body Movement

Accelerometers mounted to the body measure changes in the ride. These accelerometers are typically mounted to the strut towers. These sensors output information as gravitational forces, or “G-force” to a module. Changes in body roll due to cornering will produce lower G-force than a pothole would.

Information from the accelerometers is coupled with data from the ride-height sensor, steering sensor and other inputs by a computer processor in a module. The module can determine if the vehicle is going around a corner or traveling down a bumpy road. With this datastream, the valving inside the dampener can be adjusted in milliseconds for the best control and ride quality.

The accelerometers on the body differ from vehicle to vehicle. Some manufacturers mount the sensors under the headlights, on strut towers and near the tail lights. More sophisticated systems use more than two accelerometers mounted in various locations.

active shocks struts control module

Control Module

The control module for the electronic dampeners needs more than the movement of the wheels and body to determine the correct settings for the dampeners. The module uses and shares information with the anti-lock braking system, engine control module and instrument cluster. This information is typically shared on the high-speed CAN serial data bus. On some BMW 7-Series models, the information is shared on the fiber-optic Flex Ray bus.

With all this information, the module can do some amazing things with the adjustable dampeners. Problems like nosedive under braking, torque steer and understeer on front-wheel-drive vehicles can be minimized. If the vehicle has air ride, the volume and pressure inside the air springs can also be tuned along with the valving in the dampeners to optimize ride quality and control.

  • Tags:
  • electronic suspension
  • Shocks and Struts
Search for:
Show Full Article
Do you currently offer keyless entry programming services to your customers?


Copyright © 2019 Babcox Media, Inc. All Rights Reserved
  • Privacy Policy
  • Home
  • Brakes
  • Chassis
  • DriveTrain
  • Exhaust
  • Tire
  • Video
  • Podcasts
  • News
  • Webinars
  • Magazine Archive
  • Advertise
  • Subscribe
  • Contact Us