[Automatic] Suspension Control by Shimano

In this article, we’ll be discussing a Control Device, Suspension, and Method for Controlling Suspension and Control Device; both by Shimano, US publication 20210107588 and 20210107589. The publication date is April 15th, 2021 and the filing date is Sept 28th and 29th, 2020.

This article will be about two very similar patents, released on the same day.

Brief Summary (tl;dr)

Shimano are developing an automatic suspension adjustment system for both damper-side and air-side. For both the damper-side and air-side, the bike will be able to read whether you’re going uphill, downhill, or flat and adjust the suspension according to a lookup table stored in the programming. The damper side if just for the front suspension and will shorten the stroke as you go up a hill. The air-side is for both front and rear suspension and will adjust both stroke and sag.


I’m going to copy this part of this from my Live Valve article.

An active system receives an input and then changes the way a component reacts to the input. An active system many of us deal with regularly is an All Wheel Drive (AWD) system in a car. The AWD system contains wheel speed sensors and automatically adjusts power between the wheels during a slip scenario, for optimized grip, by locking differentials (Torsen) or activating clutch packs (Haldex), among other methods.

Alternatively, a passive system is a system that does not react to an input situation. A passive system that many others deal with regularly is a 4×4 system used in trucks. These systems have open differentials, no sensors, and locking of differentials is a manual operation performed by the driver. There are advantages and disadvantages to both systems, but I won’t discuss them here. There’s a ton of articles across the internet for that.

In the Live Valve system, the process is fairly simple from a high-level view. The system takes input from a few sensors (terrain, pitch, etc), processes the inputs in a computer (algo-magic), and sends an output to adjust the suspension based on how the engineers have determined the bike should respond for improved performance (damper adjustments).


This system is not like Live Valve. Not even close. Shimano’s system is kind of active system, and is for both damper and air-side. In reality, it’s just an automatic stroke/sag adjustment. On the damper-side, the stroke is adjusted based on the adjustment of fluid in different chambers. On the air-side, the stroke and sag are adjusted based on the adjustment of air in different chambers. Same idea, different flavors.

The damper-side idea is trying to shorten the fork when climbing and extends the fork when in any other situation (flat, downhill) using a single valve and 2 fluid chambers.

In one example, for a case where the human-powered vehicle 10 is traveling uphill or about to start traveling uphill, the position of the second member 44B is determined as being suitable if the distance corresponding to the relative position information is short.

On the air-side, there are 3 air chambers and 2 valving systems. The 2 valving systems control the suspension and, again, will determine if you’re going uphill or downhill to adjust the bike for an optimal ride based on a predetermined lookup table.


First, this whole system can be wireless

(Damper)The controller 52 and the storage 54 establish communication with the detector 56 and the adjustment unit 60 through wireless or wired connection… (Air) The control device 50 controls the adjusting device 60 through wireless or wired communication.

Damper-side: Shimano only explain the front suspension, not the rear. In short, there are four primary steps: a detection step, a comparing step, a controlling step, and an evaluation step.

Detection: The system detects relative fork position. Comparing: The system compares the fork position to a table and determines if the position is correct for optimal climbing. Controlling: The valve is opened and closed to reach an optimal fork position based on the input sensed information. Evaluation: The system checks whether the resulting adjustment is correct and readjusts if not.

FIG. 2 shows the controller system for the damper side. The suspension system includes an operation device 70 and a detection device 80. The operation device (not important) outputs information from the user (is there a rider?) to the control device. The detection device obtains traveling information of the bike. For example, the traveling information can be inclination with respect to pitch, cadence, torque, speed, acceleration, power, etc. So, the detection device is just a bunch of sensor information with respect to inclination.

The control device is what tells the actuator to adjust the suspension. The controller takes the sensed data from the sensors, uses a predetermined lookup table to determine the correct position of the fork, sends that information to the actuator, and then the front fork changes position.

The control device 50 further includes a storage 54 that stores table data indicating a corresponding relationship of predetermined relative position information and a predetermined relative movable amount. The storage 54 stores information used for various types of control programs and control processes.

This sensor is not to be confused with the detector. The detector determines the relative position of the stanchion and lower. This can be an optical sensor, potentiometer, etc. This just determines the L1 value in FIG. 5.

Figure 4 shows the damper itself. 44A is the lower, 44B is the stanchion, 60 is the adjustment unit (vague arrow pointing to the middle). C1 and C2 are fluid chambers, and R1 is the fluid flow path between the chambers.

This is where the control device comes into play. It tells the adjustment unit 60 where/how to move fluid. Then, when the computer calculates all the input information from the sensors, it determines whether to open and close valve 62, which opens and closes fluid between chambers C1 and C2. The valve has a little motor to open/close.

Lastly, the system will double-check if the adjustment was correct. It’ll take the pre-adjustment and post-adjustment distances (L1), then compare them to the table and determines whether or not to continue adjusting. So, if the system gets it right the first time, there will be no need to readjust. I assume this will happen in microseconds.

Air-side: There appear to be only three steps here: detect, compare, and control. There isn’t an evaluation step.

So, the air-side system is for front and rear suspension, which will work exactly the same. I’ll just say “suspension” so we don’t get confused.

First, this system will set your sag by either changing the overall length of the suspension or changing the volume of the air chamber, or both. I’m not giving up travel, so I’m taking the second one.

In a first example, the adjusting device 60 is configured to adjust the initial sag amount of the suspension 44 by changing an overall length of the suspension 44… In a second example, the adjusting device 60 is configured to adjust the initial sag amount of suspension 44 by changing a volume of the chamber 44C.

FIG. 2 shows the electronic system. The detection device will detect things like axial load, speed, torque, etc. and output the sensed information to the control device, which contains a controller. The control device will tell the suspension how to adjust based on what the bike is feeling. In the end, all these sensors determine if the bike is going uphill, flat, or downhill. Nothing more.

Notice how many more blocks there are in this document compared to the damper side. In reality, it’ll should be almost identical to the damper. These documents were probably prepared by different people, and this is how they wanted to show the system.

As with the damper-side, the air-side has valves to allow air to flow between the three chambers. More importantly, there are two different valving systems in this one. 44D is the upper chamber, 44C1 is the middle chamber, and 44C2 is the lower chamber.

As shown in FIG. 5, the upper valve system (44D -> 44C1) controls the length of the suspension, and the lower valve system (44C2 -> 44C1) controls the volume of the chamber 44C, which should control sag. I’m fairly sure about the sag, but Shimano don’t say, so I’m just assuming. I’m also assuming that little unmarked nipple thing at the bottom of FIG. 5 is a valve of some sort.

So, the bike will determine if you’re riding uphill or downhill based on the sensed information and adjusts the amount of air between the chambers to optimize the ride. The adjustment is performed by valves 61 and 63. It’s important to note that the adjustments are not made via any AI system, just a standard lookup table that is preset by Shimano.

As with any lookup table and wireless system, though they don’t say it, Shimano will absolutely be able to data log and adjust the lookup table as they gather information.


Ultimately, this system automatically adjusts damper fluid and air pressures to provide a better climbing platform. As far as the damper-side goes, Shimano state the stroke will shorten on climbs and go back to normal on flat/downhill. As far as the air-side goes, they don’t give a single example scenario, but I’m going to assume that if you’re going uphill, it’ll also shorten your stroke and probably try to stiffen up the system.

It’s anyone’s guess whether this works or not. It appears to be high level, so there may be some intricacies we’re missing. Either way, Shimano are trying to develop suspension systems for active bikes. Lastly, this whole situation looks like an absolute nightmare to service.

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