Dissecting Shimano's Patented Anti-Dive Suspension Control Device 23

By Daniel Bacon, Wheelbased

Suspension Control Device for a Human-Powered Vehicle by Shimano

In this article, we’ll be discussing a Suspension Control Device for a Human-Powered Vehicle by Shimano, US patent 10,882,582. The patent date is Jan 5th, 2021 and the filing date is July 13th 2018.

This is another active suspension patent from Shimano, this time for anti-dive situations.

Brief Summary (tl;dr)

Shimano are introducing an active anti-dive system based on the pressure applied to the brake lever and stroke of a brake pad. As the rider hits the brakes, the bike will want to dive forward, compressing the fork and extending the rear shock. This system will sense the brake forces and adjust the front and rear suspension to compensate for the diving forces, so the bike will (hopefully) stay as flat as possible. This will reduce the likelihood of going over the bars, preserve braking performance, and add a new level of stability to the bike.

Background

We’re talking about an active system again. Based on the patents I’m reading, active systems may be very prevalent in bikes in the coming years. Below is an exerpt from my Fox 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 4x4 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 are plenty of articles across the internet for that.

In an example scenario, let’s think about a non-aero car. When you hit the brakes, forward momentum will cause the car to dive forward, called pitching forward. When this happens, weight is transferred away from the rear tires and toward the front tires. This can cause a ‘loose’ scenario when turning, if turning and braking occur at the same time, so it's likely to lose the back end of the car and spin out of control. This is a passive system, where the car does not react to an input scenario.

Now, let’s introduce a scenario where the car has a hypothetical active anti-dive system. There are sensors inside the suspension system, brake pedal, steering wheel, etc., that sense inputs. There are also servos, motors, etc., to adjust valves, compression ratios, etc., inside the suspension system. When a driver hits the brakes, the car will know the speed and position of the brake pedal, the speed of the car, and various other inputs that will affect the pitch of the car. This hypothetical anti-dive system will receive the inputs from the sensors, send the received inputs to a computer that then calculate an optimized anti-dive output. The computer then tells the suspension motors, servos, or valves what to do. So, the computer should tell the front dampers to close the compression circuits as much as possible to keep the nose in place. The computer will also tell the rear dampers to close the rebound circuit as much as possible to keep the tail in place. The end result would be a much flatter car with weight transfer minimized and grip preserved. All of this is performed without manual input from the driver. This is just an example scenario and these actions can be performed using other methods such as mag-fluid, air pressure adjustments, or linear actuators that actually move the car.

Introduction

Anti-dive systems have been used in motorcycles in the past. Older mechanical anti-dive systems would hydraulically connect the brake fluid to a damper control, and they typically worked well enough.

In electronic-based active systems, sensors can sense braking forces, speed, and pitch of a bike, among other inputs. The system is programmed with algorithms, where super-smart engineers have figured out ideal settings for the suspension to prevent the bike from diving and staying in a flatter state. Valves will open and close to prevent or allow the suspension to move at certain rates to keep the bike in place during braking.

Here’s a cool article about an Aprilia patent, where they created a linkage structure to alleviate the anti-dive situation. It’s important to note that Aprilia is solving the issue with a passive system, where Shimano’s system is active. But why are Aprilia using a passive system? Because MotoGP banned active electronic systems in 2010, just like the FIA in 1994. Hmmm...wonder why? Off on a tangent, but it appears Ducati has figured out a way around that ban using a secondary hydraulic system that the writer is saying is similar to Canyon’s Shapeshifter. Secondary meaning no rider input, and hydraulic meaning no electronics. So, it’s active but not electronic, so it gets around MotoGP rules. Nice.

Intended Novelty

This is another patent where the minutiae of the intended novelty probably isn’t really important. It sounds like the novelty is the use of both a sensor in the lever and in the caliper to either compare braking between the two sensors, or use either/or sensor, in the calculation of how much suspension control to apply. The real implication here is active suspension control based on braking forces in a bike.

Why?

As with every other Shimano patent, they don’t say shit about why they do anything, but they do say this:

With the suspension control device according to the first aspect, it is possible to improve the running performance (e.g., stability) of a human-powered vehicle by controlling a suspension in accordance with an actuation of a braking system.

Super vague, right?

Heavy braking, especially front braking, will cause a bucking-type scenario, where the front end will dive, and the back end will extend. The result can be a Friday Fails-type over-the-bars crash. Additionally, heavy braking will cause the back end to lose grip, possibly reducing overall braking ability. So, in the end, this is being developed to keep people from launching over the bars and keeping the bike nice and tight during braking for stability and (possibly) better grip.

What?

Shimano’s system uses sensors and an electronic controller. The sensors will sense the actuation of the brakes and the pitch of the bike, and the controller controls the suspension system based on what the sensor senses. There are algorithms saved into the controller that determines how much suspension control to apply to keep the bike in place.

In short, Figure 8 shows a flowchart of what they’re doing. Figure 8 shows stroke adjustments, but it could be damping control, spring control, or anything else that might control the suspension. Let’s go through S1, S2, and S4. If the rider is applying the brakes and the bike is tilting forward, the front and rear suspension strokes are adjusted according to what the controller tells the suspension to do. In this case, the stroke is increased in the fork and the stroke is decreased in the rear shock.

How?

Figure 2 shows an example handlebar situation. First, component 14 is a ‘user input device’, where the user can use the user input device to move the suspension manually with the flick of a switch. But this isn’t really important here — it’s just a manual override where you can actually move the suspension with a switch.

…user input device 14 [is] for manually controlling and/or setting the front suspension FS and the rear suspension RS of the suspension control device 12.

Lets get into the meat of it.

In figure 2, components 40 and 44 are sensors to detect front and rear brake lever movement, respectively. As the rider grabs the brake lever, those little sensors send a signal to the controller that says “Hey, this dude is pulling on me. You should do something about that”.

There is also a secondary braking sensor system that detects the amount of brake pad movement. Figures 3 and 4 show the front and rear braking assemblies. Components 42 and 46 are the brake pad sensors located in the calipers that detects actual brake pad movement. It appears as though the braking calculation takes both the lever actuation and actual brake pad movement into account when determining what to do with the suspension system. Pretty nifty right there.

So, we’ve got sensors that sense brake pressure, but what about the actual pitch of the bike? That seems like an important piece of the puzzle.

There is also a sensor 50 (shown in Fig. 1 above) that sends a signal about the pitch of a bike, or the change in pitch, to the controller to determine how to adjust the suspension. So this sensor also tells the controller “uhhm, hey, we’re starting to pitch forward, please do something about that”. The sensor can be and accelerometer, an inclinometer, a tiltmeter, etc.

Using the [accelerometer, an inclinometer, a tiltmeter, etc] 50, the electronic controller 16 can determine whether the traveling inclination of the [bike] is in a nose dive state, a downhill traveling state or an uphill traveling state.

Component 16 is the controller. The controller takes input from the brake sensors and the pitch sensor and tells the suspension what to do. So, in this part, the controller goes “okay, you heavy-handed gorilla, I received your input. I’ll let the suspension know to stop that shit”. Shimano describes the controller as supplying a voltage to the actuators or motors in the suspension to automatically adjust the suspension:

…the electronic controller 16… supplies electrical power from the power supply B to the electrical components such as the actuators or motors of the front and rear suspensions FS and RS.

In the end, the system can sense brake application in both the lever and the brake pads, and also senses the pitch of the bike, whether the rider is braking or if the rider is just riding up or down a hill. The signals are sent to a controller, that then sends a signal to the suspension to open/close actuators in the suspension to control the movement of suspension travel while braking.

As far as the actual mechanism of suspension control, the suspension has 4 possible components controlling the movement of the suspension: A lockout state actuator, a stroke adjustment actuator, a damping force actuator, and a spring force adjustment actuator. In the end, one or all of these can be used to adjust the suspension.

Shimano state how the front suspension will be controlled, but the rear suspension is exactly the same:

Preferably, each of the actuators are electrically controlled actuators that include an electric motor or an electric solenoid that is either located on the front suspension or remotely located. In this way, the electronic controller 16 can control the actuators to adjust the front suspension FS based on actuation of a braking system and/or the traveling state of the [bike]. While the front suspension FS is configured such that a lockout state, a stroke, a damping force and a spring force are all adjustable, it will be apparent from this disclosure that the front suspension FS can be configured so that one or more of these adjustments are omitted

Shimano don’t talk much about the actual actuation of the suspension system, as that will probably be in another patent (or multiple other patents). In the end, that’s not important here, since they’re just showing a total system to control those little actuators using the brakes and a little controller.

Conclusion

There's a clear pattern in the cycling industry with recent patents — active systems are coming, whether you like it or not. From a technical perspective, this is a cool concept. With the addition of all of these little active-bike patents, we’ll eventually have a bike that’ll ride itself like a roller coaster.

Would you use or want technology like this? I’d actually like to see how it feels, but I’m still going to be a dickhead purist, and say I don’t want this in my bike. I really do not want engineers controlling how my bike feels based on the algos they’ve determined as ‘optimal’. That being said, I will take it in my car, and I absolutely see the reason for it in bicycles. This type of technology will excite many people.

How cool would it be to go full gas into a turn, slam the brakes, and NOT have the bike pitch forward. You won’t have to send your body backward to compensate for your weight diving forward and possibly grind down your ass on the rear tire. I’ve done it, it sucks. Just hit the brakes and the bike does exactly what it should do.