Question:
What can I do for gearbox control, there are a lot of products on the market and it is very confusing?
I will give you a little bit more information on the gear change systems and how they work, then hopefully this will give you an idea of what can be done and what the pitfalls are if your system is too simple.
Answer:
I decided to design a gearbox control system in 2003 and it was ready to run for the beginning of the 2004 season. When we initially tested the car, all seemed fine. But as we got to the first event and subsequent events we discovered the gear changes were becoming erratic and as the season progressed, the changes got worse and worse. I looked at the systems before designing ours to see what everybody was doing and assumed that a Gearchange was simply a question of cutting the spark and then pushing it from one gear to the other. At the end of the 2004 season I removed the electronic system and put a manual system onto the car, similar to that you have seen on our web site using a cable or rod operated system which was connected directly to the gearbox. I logged all the information over the season to discover what was going on. We found out that no two gear changes ever take the same amount of time, no matter what the conditions and if the vehicle happens to be wheel spinning, gear changes take even longer.
When you are driving with a gear stick or gear lever or anything where the driver or rider is connected directly to the gearbox, without realising every time you carry out a gear change you actually subconsciously adjust the way you change gear, whether it be foot or hand operated clutch. So when you produce an electronic system to reproduce this, a simple system which we had originally come up with is not capable of doing this. If you simply put a long time for the spark to be cut and the gear changes faster, the gear changes feel as if they take forever and if you put a short time in there, quite often a gear can be missed and the gearbox will become damaged if not straight away over time. So we very quickly learnt that you need to produce full closed loop system which works out drum rotation of the gearbox and therefore the time for the power reduction of the engine can be varied according to how fast the gear change occurs, therefore making a self-adjusting system.
This is just a basic explanation of how it works. Our system is actually considerably more complex than that, so it can actually work out if the gearbox is actually going to change gear, what to do if it doesn’t want to change gear and so on. Next comes the mechanism that you are using to change gear. When you change gear with a bike or car gearbox, you never actually kick it into gear, or smash the gear stick into gear, you actually feel it going into gear smoothly. So the system you use to carry out the gear change needs to be able to give a gentle, yet precise and smooth operation without damaging the gearbox itself. It is not a question of how much power or how fast you can move the stick, as you would simply damage the transmission.
I spent a further 5 years designing and testing our system, so that now that once it is set up it can self-adjust to suit most gearboxes. But this involves quite a few complex components and a powerful ECU that controls not only the engine but the gearbox itself. In fact to give you an idea of how complex it is, if the system senses that the gearbox does not want to change gear, due to the fact that the dogs are jammed or locked for any reason, because the ECU that controls the engine also controls the gearbox, it can do very precise control. So sometimes it fires one spark or removes 1 spark in order to unlock the dogs. This would be impossible for a piggy back system or standard ECU as it cannot know when each spark is going to be delivered.
There are a few high quality systems available on the market which are extremely good, but they are not cheap. The simple system that is listed on our web site which uses the original gear stick or cable is a fairly basic design and allows you to go for faster gear changes, but because of the driver actually being able to feel the gear changing through the lever or paddle, this adjust how the gear change occurs. Any system that is fully electronic e.g. where the driver is not directly connected to the gearbox, would need to be a closed loop design to function correctly in all conditions. With a simple system that simplifies a solenoid or actuator has its limitations and maybe ideal for use with a driver who is disabled or for casual driving where the user understands its short comings.
This is why we only produce the two types of system. Either one where the driver is still directly connected to the gearbox by a mechanical mechanism or a full gearbox control system.
2021 Update: The gearbox control strategy has been completely rebuilt and redesigned from top to bottom using everything that has been learnt in the past to produce a more advanced system to further improve gearbox control. The biggest change is that we now use rev matching, this means that the ECU looks at its next target gear and calculates from gear ratios as to what the rpm needs to be for the next gear and then once the gearchange begins, the rpm is then matched to its target gear, but obviously once the gear change has started effectively the two halves of the gearbox become detached from one another and on the more advanced set ups, which we recommend with 4 wheel speeds, the ECU is then able to work out from the driven wheel speed information the exact rpm required, even if the wheel speeds change during the shift e.g. if you are wheel spinning during the change, the driven wheels would then slow down and the ECU would adjust the rpm to ensure the revs are correct to go into the gear. The same would apply if you lock momentarily the driven wheels whilst downshifting, so the ECU is always accounting for the actual speed that the target gear that is asked for.
Category:
Gearbox & Clutch