MotoMojo: Electronic Suspension

Oct 07, 2016 View Comments by

Electronics have gotten into almost everything, and we can expect even more integration of microchips into our daily lives in the future. Light weight, instantaneous response, compact size, and relatively low cost have driven this revolution.

Motorcycle manufacturers have followed the auto industry, introducing electronic controls for ignition systems, electronic fuel injection, ABS, and now suspension. These chassis systems provide a greater amount of control for improved cornering, acceleration, braking performance, and comfort.

Defining the Systems
There are several loose categories of electronically controlled suspensions (ECS). Active suspension “actively” controls vertical wheel movement relative to the chassis, as compared to passive suspension, which moves entirely in reaction to the road surface. Electronic suspensions are generally divided into pure active, adaptive, and semi-active.

esa-2True active suspension uses hydraulic rams to directly control wheel travel by lifting it for a bump or pushing down into a low spot, while maintaining as level a vehicle as possible. A true semi-active system utilizes electronically controlled valves in the suspension components to make damping changes in milliseconds. An onboard microprocessor uses sensors to measure input data to control active and semi-active suspensions. Currently, it is too costly and requires too much weight to operate true active systems for motorcycles.

ECS systems work by attaching small servomotors to the fork and shock adjusters. These servos vary damping (and in some cases preload) to a rider-selected mode. Adaptive suspensions vary shock absorber damping rates to “adapt” to road or riding conditions. Unfortunately, the slow response time (tenths of a second—as opposed to milliseconds) limits the action to general riding conditions rather than specific bumps.

Several motorcycle manufacturers have introduced semi-active ECS. One of the first was BMW, with its electronic suspension adjustment (ESA) system on the K 1200 S. This optional feature enables the rider to adapt the motorcycle chassis to riding style, load, and road conditions. Using a button on the left handlebar, the rider can vary preload and damping characteristics of the front and rear suspension. On the R 1200 GS, ride height can be adjusted for terrain conditions.

electronic suspensionBMW uses sensors to measure front and rear suspension position, along with the rate the suspension is moving up and down. Information from the ABS wheel speed sensors and the lean-angle sensor also help the computer decide how to adjust the damping control valves in the fork and rear shock. A stepper motor varies shock control valve opening to vary damping rates. The goal of the system is to be transparent. Once set properly for conditions, you are unlikely to notice its operation.

Ducati was another pioneer. Ducati Skyhook Suspension (DSS) uses four accelerometers to detect vertical velocities, and this information is fed into the computer, to be used by the Skyhook algorithm. It also relies on data from the ABS and traction control systems to calculate damping settings. Yamaha introduced ECS on the FJR1300ES. The system adjusts fork damping along with damping and spring preload at the rear shock. Four preload settings are available. With each, three damping settings are available. Riders can then adjust damping from three firmer to three softer.

Several years ago, Öhlins launched the first electronically controlled (EC) shock absorber for the hypersport motorcycle segment. This Mechatronic shock, designed for the Kawasaki ZX-10R, was the first-ever for a motorcycle that wasn’t manufactured with ECS. There are now several aftermarket manufacturers providing suspension components that can replace OEM shocks and are compatible with the existing electronic controls. Among these are Tractive and Wilbers.


Magnetorheological Damping
Another method of controlling shock absorbers is magnetorheological damping, developed by Delphi Automotive under the name MagneRide for General Motors. The shock fluid contains metallic particles, and an onboard computer rapidly adjusts the shock’s damping characteristics by varying current flow into the shock’s magnetic flux. This causes tiny metal particles in the fluid to change alignment, which varies effective fluid viscosity, thereby changing compression and rebound rates without changing the orifices.

This method may soon see use in motorcycles. Future electronic systems are likely to adjust ride height in anticipation of hard braking to keep the bike stable and to allow easier turn-in, along with a host of other features that we haven’t even imagined yet.

Text: Ken Freund
Photography: Ken Freund, Öhlins, and Touratech


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