DIY Anti-lock Braking System

anti-lock braking system or abs for sure you most likely heard about it and if you drive a car or modern motorbike you've probably used it before but how does it actually work how do anti-lock brakes work ABS uses wield speed sensors to determine if one or more wheels are trying to lock up during braking if a wheel tries to lock up a series of hydraulic valves at limit or reduce the braking on that wheel this prevents skidding and allows you to maintain steering control seems simple enough [Music] [Applause] I set about 3d printing and CNC cutting various parts of the mechanism that would be able to release attention in cable operated breaks the reason for choosing cable operated breaks was because I didn't want to mess with the hydraulic brakes on my newer DIY electric bike plus the bike I want to test this on has now a row ties in the hope they will have minimal grip on bad services but it wasn't long until I encountered my first issue so this is the ABS mechanism which will release the tension in the brake cable but there's one major one major flaw with this design in that the stepper motor is not strong enough I originally ran this stepper motor which has 1.2 Newton meters of torque this new one has 2.8 Newton meters of torque and it still isn't enough to hold the brake tension if I pull the rear brake it loses steps so I'm gonna have to redesign this whole mechanism I've been redesigned the mechanism to give the stepper motor a greater mechanical advantage using different lever lengths this meant the motor had to rotate further but also applied more force to counteract the tension in the cable caused by my hand which would also mean the response time will be slightly longer but that was the least of my worries because I didn't realize how terrible rim brakes were after riding on wet grass I wanted to test the system on the rear wheel and only way I could get it to lock up was by shifting my weight upwards and forwards temporarily to lift the rear wheel off the ground which was pretty far from ideal so after adjusting the mechanism about four different times I decided to scrap that and move to a bike with hydraulic disc brakes if you're one of my subscribers you'll most likely recognize this as my homemade electric bike before this video I've removed the drivetrain as the high voltage batteries were interfering with the ABS electronics to accurately measure the speed of the wheel I've made this 3d printed disc with 120 slots in it mounted to the fork is a sensor which has an infrared beam and this infrared beam shines through the slots in the disc when the wheel spins and the beam is either broken or made the sensor outputs a high or low signal this can then be used to calculate the speed of the wheel up to 50 times per second interestingly enough I noticed this exact same speed measuring technique being used on a motorbike with an anti-lock braking system moving up the frame there is a black box which contains the electronics which will control the ABS system inside the black box is a tint see three-point-six board which will run the Arduino code and it also has an SD card slot so I can do data logging of the tests to hopefully optimize the system when the Arduino code realizes the break needs to be released it sends pulses to the stepper motor driver which is inside this large heatsink that then sends power up to the motor mounted on the handlebars to rotate the mechanism to release the brake is really simple it's just a long lever which is clamped to the brake lever that is attached to a short bit of rope the Rope will allow the brake to be used as it normally does but when required will allow the motor to winch the brake lever opposing the force from my hand and releasing the brake before I give the system a test let's talk about how the activation of an anti-lock braking system might actually work so you have a vehicle traveling along at a constant speed and the rotational speed of the wheel is relative so that the outermost part of the tire is moving backwards at the same speed as the road is relative to the car when the brakes are applied if the friction between the tire and the road is too low the wheels will slide but how does the ABS electronics actually detect this and know the will is definitely sliding it's actually quite a complex question to answer so let's work towards it using a few somewhat logical approaches first an initial observation will be to that the wheel is sliding when the speed of the wheel equals zero when the wheel stops rotating and because I've got a speed sensor on the front wheel of my bike what I can do is I can program the electronics to release the brake when the speed goes to zero now what I'm actually going to do is program it to release the brake when the speed is below 0.5 meters per second it's about just over 1 miles per hour and the reason for this is sometimes a sensor might read 0.0001 meters per second and won't release the brake so the brake will be released when at the speed is below 0.5 meter per second this gives us a test okay so those tests were pretty successful it proves that the mechanism is able to release the brake pressure from my hand and get the wheel spinning again the only problem is that it was very slow the time taken from when the wheel had fully locked to when the stepper motor started to winch the brake lever back was about zero point two two seconds and the total time that the wheel was locked for was zero point four five seconds so the wheel was skidding for almost half a second in terms of the mechanical response time which is the time taken for the motor to rotate and pull the leave it away from my hand that's gonna be very difficult to improve without extending my budget even further I've already bought two different stepper motors for this project and to buy the next step up and talk is going to cost way more than I want to spend on this project so what I'm going to try and do is focus more on the electronic response time these stepper motor takes about a quarter of a second to react and fully release the brake so if we can take that electronic delay time down then hopefully we should be able to get a pretty good anti locking brake system so how can we detect that the wheel is going to skid before it actually happens well let's take a look at the data logging this graph shows the speed of the wheel over time and we can see there is a large drop in speed as the wheel logs when the speed is below 0.5 m/s the brake releases if then speeds back up to match the speed of the bike and the brake is reapplied when the speed is greater than 0.5 m/s so to improve the response time we need to trigger the brake release right at this point on a graph let's see if not in the deceleration of the wheel will give us a better indication this acceleration graph shows three clear troughs and peaks which display when the wheel is either slowing down to a skid or speeding up to match the speed of the bike how about we set a deceleration limit which will trigger the brake release for example if the wheel decelerates quicker then minus 10 meters per second squared the brake will release this time the stepper took 0.11 seconds to start moving which meant we've cut the electronic response time in half but there was a small issue it only fully released a break once okay that time it released twice but it still didn't release on the final skid maybe third time's the charm right analyze the data and the slow motion footage and what I've realized is that the deceleration is just a peak value or well a trough value because it's negative but basically what this means is that we break only releases temporarily it doesn't hold the brake open until the wheel speed increases again so as soon as it detects the deceleration going really low it basically just releases a break and puts it back on instantly and then doesn't allow the wheel enough time to get back up to speed before reapplying the brake this could be fixed by adding a small delay to how long the brake is disengaged for for example the bread could be disengaged for a quarter of a second so the brake gets released and then it waits for the wheel to get back up to speed and then it's reapplied again but the problem is of this is that in some conditions the brake may just be deactivated for a quarter of a second for no reason and could therefore extend the braking distance of the bike so by now you're probably reconsidering how simple anti-lock braking systems actually are and before I did the research for this video I actually thought the same thing now throughout my research I found many many different solutions of how you can detect when the wheel is about to skid before actually does but the majority of them all seem to boil down to one variable called the slip ratio the slip ratio is the ratio of the speed of the wheel versus the forward speed of the car if the wheel isn't skidding so it has full grip with the road beneath it then the slip ratio will be zero if the wheel speed is zero so it's fully locked and it's sliding across the road then the slip ratio is 1 now the ideal slip ratio will depend on many different factors and if you search slip ratio into Google you'll most likely see a graph that looks like this now what this graph means is that the slip ratio can have a small range where the wheel can actually rotate slightly slower than the forward speed of the vehicle but if it goes outside of this range where the wheel speed is much slower than the forward speed of the vehicle then the will must be coming to a stop and therefore going to start skidding so that sounds pretty simple then if the wheel is spinning slower then the bike is moving forwards then I just need to release the brake pressure and I should be able to stay in control but unfortunately it's not that easy because I can't easily measure the forward speed of the bike if a wheel is sliding with a car you have four wheels so if one wheel slides you then have three other wheels to measure the forward speed of the car which you can compare those three wheels to the world sliding and release the brake on that wheel but with a bike because the front wheel is the most important wheel not to slide you only have the rear wheel as a reference and if that rear wheel lifts off the ground or locks itself you now have no other reference to detect or measure how fast the bike is traveling forwards so here's my plan inside the box where I mounted the electronics I also mounted an accelerometer this will be used to measure the deceleration of the bike now what it's going to do is when I press the front brake there will be a deceleration which will enable ABS activation mode what this will do is it will save the initial speed of the wheel before it starts skidding and it will also start the timer now because we can calculate speed by multiplying acceleration by time we can then take the initial speed and subtract the acceleration times the measured time from that period so we can basically estimate the speed of the bike going forwards from that initial ABS activation point this is all theory but because I've had the accelerometer mounted on the bike from the start I've actually applied this theory to the previous data logs of the other tests and it's looking pretty promising so what I'm going to do is set it up to release the brake when the speed of the wheel is below this estimated speed of the bike because then it must be skidding so what I'm going to do is I'm going to write the code to program into the bike and then we can give it a test that look pretty good to me let's give it another few tests to check the reliability that works okay so that was three successful tests in a row all in control let's check the data and slow-motion footage from the three tests carried out using the slip ratio triggered break release the average time from the wheel stopping to the motor moving was 0.08 three seconds and the full wheel lock to release time being zero point three one one seconds meaning this accelerometer estimated slip ratio control system is about 30% faster than the zero speed triggered system which considering 0.2 four seconds of that time is taken for the motor to rotate the actual response time of the electronics itself was three times quicker I realized this thing isn't quite enough to prevent the wheel from locking but according to the data I've received to release the brake before the wheel comes to a stop the whole system would need to detect what's happening and release the brake in 0.08 of a second sure this might be possible with a larger budget and more skilled electronic engineers but for these tests skidding for one third of a second in an upright position was very feasible in terms of control now you might be thinking what about different services well the snow isn't coming back anytime soon so I decided to try a few different services that might be experienced during everyday riding [Music] this made me question do you really need an anti-lock braking system on a bicycle in fact I don't remember the last time I've crashed a bike purely due to braking alone obviously ignoring the test in this video which I think is important to think about because an anti-lock braking system on a bicycle won't guarantee grip on that front wheel for example if you go around the corner too quickly and have to lean over too far on a less than perfect surface that front wheel can still lose grip and the ABS won't do anything to save you I think abs on a motorbike is a completely different story because motorbikes careful for quicker and they're also more likely to you have to do emergency stops also the cost of an anti-lock braking system on a motorbike is far less of a percentage of the overall cost of the vehicle versus putting it onto a bicycle which also has to be questioned if you want to say that an anti-lock braking system is good for inexperienced cyclists because they probably aren't that many inexperienced cyclists that will be willing to invest the amount of money required to have an anti-lock braking system Bashi released an anti-lock braking system for some of their electric bikes in 2018 and they even integrated an anti over the handlebar system where basically as soon as the rear wheel lifts off the ground it will then release the brake to prevent you going over the handlebars now interestingly enough I can also implement this onto my bike because the accelerometer unit also has some jurors and I read a review of the Bosch ebike system on a bike MTB comm and they said the ABS ebike from bosch is the perfect solution for rental ebikes ie for tourists and I think this is a great point because I don't believe there are many people out there that's an inexperienced cyclist that's are willing to spend the amount of money you need to spend to get a bike with an ABS unit but for tourists that may be inexperienced of cycling I think it's perfect so I suppose that concludes this video it's been about four weeks to research design make this project test it most of it was troubleshooting all the issues with the motor not having enough talk and also errors in electronic code it drove me a bit crazy at points but it was a pretty enjoy enjoyable if you enjoyed this video it'd be appreciated if you could leave a thumbs up if you're new to much I don't want to see similar videos obviously different topics but you know other engineering type videos please click Subscribe down below I need to say a massive thank you to all of my patrons for supporting me throughout this full week period all of this work I was uploading various update videos on the project as I went along and the questions that you guys had over on patreon really helped me steer into the right direction of what people wanted to know in terms of the topics and also you guys gave some great suggestions in terms of getting on the right track because I got lost in the information at points yeah so thank you very much for watching and I'll see in the next video goodbye

Channel: Tom Stanton

Views: 1,771,971

Keywords: bike, bicycle, cycle, cyclist, ABS, anti-lock brakes, anti-lock braking system, anti-lock braking system (abs), vehicle, electronic, arduino, code, physics, engineering, automotive, engineer, DIY, homemade, electric bike, science, data, funny, dirt bike, skid, crash, bike crash, bike fails, disk brake, hydraulic, braking, anti, lock, brake, system, mtb

Id: iiRpGHiKHJ0

Length: 20min 5sec (1205 seconds)

Published: Fri Feb 15 2019