Most people find running on treadmills to be incredibly boring. However, self-regulating treadmills can take the monotony out of typical indoor exercise. Treadmill technology has increased in the last decade to include features such as heart rate sensors, calorie counters, and even TVs. However, the runner has always been constrained to running at a constant uniform pace. The runner has to pick their speed and adjust to that. This is not compatible with the natural variation in pace that runners experience outside. Self regulating treadmills have already been researched, prototyped and tested however they have not been commercialized or patented yet. These treadmills are able to detect the speed of the runner on the treadmill in order to control the pace of the running belt below the runner’s feet. When the runner speed up, the belt’s speed will increase. The opposite is also true. When the runner slows down, the belt will decrease its speed.
This additional control is not vital to the function of the treadmill. However, the additive feature gives the runner the freedom to set the pace of his or her own workout instead of being controlled by the treadmill. It is often difficult for a runner to stay at the same pace the entire time he or she is running. This treadmill allows the runner to change speed quickly without having to push buttons or set a new pace on the monitor. Additionally, according to preliminary testing, this additional feature can improve the athletic performance of the runner. When tested on both regular and self regulating treadmill, experienced runners improved their VO2 max scores (a measure of the maximum volume of oxygen an athlete can use) by 4 to 7 percent. Controlling the position of the runner on the treadmill is also important for safety reasons. If the runner were to stumble or misstep, the belt would be able to slow down to allow the runner to safely recover. Also accidents which occur when people run into or fall off the treadmill would be reduced. Some treadmills like the one below have a safety clip to try to stop the treadmill if the runner falls too far behind. However, it doesn’t prevent the runner from running too far forward. A good range of operating conditions for this parameter would keep the runner within a foot from the center of the belt.
The treadmill works by adding a sonar range finder (shown below), a transmitter, a micro-controller and a computer. The sonar finder is placed at the back of the treadmill and is used to measure the distance between the runner and the sonar finder. Typically, the sonar is aimed between the shoulder blades of the runner since the position of a runner’s legs cycles while the position of a runner’s back is relatively consistent. The sonar finder measures the distance between the runner and the sonar device. It then sends this signal through the transmitter to the micro-controller. The process uses a feedback system, which makes changes to the system based on measurements in the output. As a consequence, this forms a reactive system. The micro-controller compares the runners current distance from the back of the treadmill to the distance between the back of the treadmill and the midpoint of the treadmill. If the measured distance is larger than the compared value, the belt speeds up to bring the runner back towards the middle. Conversely, if the measured distance is smaller, the belt slows down to allow the runner a chance to catch back up to the center.
The controlled variable is the distance between the runner and the back of the treadmill. In order to control the distance, the treadmill manipulates the speed of the belt via the mechanical work done by the rotators. The range of the sonar’s distance would be from the end of the treadmill to the front of the treadmill. Other readings should be at saturation because a person has to be on the treadmill. The controller would also limit the maximum possible speed as a safety precaution. If the person’s position changes the controller should not overshoot the maximum safety limit because it might cause the runner to fall. The minimum speed of the treadmill would be zero.
Potential disturbances to the system include dramatic changes in runner velocity. If a runner were to stumble, trip or fall, their speed would be drastically reduced. Also the sonar needs to be able to tell the difference between a runner’s foot and a different object. For example if a runners water bottle fell right in front of the sensor, we wouldn’t want it to slow down too quickly thinking that the runner is too close to the sensor. Sonar sensors are already capable of differentiating between humans and other objects. Sonars send out ultrasonic sound waves that are then reflected off of people and things and returned to the sensor. The time it takes for the waves to return is used to calculate the distance. However, the intensity can be used to determine if the wave is being reflected off of a human. Several factors affect the intensity of the reflection including size and texture. Humans return ultrasound waves within a relatively small range of intensities. Therefore, if an intensity falls within this range it is extremely likely to be from a human.
The sensor would use a feedback loop. It would be hard to determine variances in the runners input. It is a lot easier to determine differences in a runner’s speed. If a runner wanted to increase his or her speed, he or she would run harder. Therefore, the runner to move forward on the treadmill. This would cause the sensor to detect the changing distance from the runner to the sensor. The sensor would transmit a signal and it would be compared with the set point signal. The controller would then speed up the treadmill until the runner is back at the set point distance.
In order to mimic the natural fluidity of running outdoors, treadmills could soon become capable of matching the runner’s pace instead of operating at a constant speed. This additional feature would improve athletic performance of the runner while hopefully creating a more exciting workout.
Works Cited
Bonar, Tom. “MaxBotix Inc., High Performance Ultrasonic Rangefinders.” Kiosk Sensor and People Detection. N.p., 07 Oct. 2012. Web. 31 Mar. 2016.
Grabmeir, Jeff. “New Design Makes Treadmill More like Running Outdoors.” News Room. N.p., 14 Apr. 2015. Web. 31 Mar. 2016.
Vergara, William C. “Science Explorations: Journey Into Space: Radar and Sonar | Scholastic.com.” Science Explorations: Journey Into Space: Radar and Sonar | Scholastic.com. N.p., n.d. Web. 31 Mar. 2016.
First of all, I LOVE this idea. I see an invention such as this becoming quickly assimilated by professional sports teams that practice in cold or inclement climates (i.e. Canada, Alaska, Washington, etc.). It would allow athletes who are typically restricted to indoor, mechanical practice an opportunity to improve their overall athletic abilities. And, with a few advancements, this treadmill will be a great tool for athletes trying to reach new goals. Since the device can easily report speeds, it would allow athletes to view in-time data reports on their performance. Athletes would be able to see exactly how fast they are running, and, consequently, challenge themselves to run faster. It could even be used to track consistency or variance. Athletes who needs to improve explosiveness can now force their bodies to speed up and slow down, rather than rely on a current treadmill to change the pace for them.
On a more average-Joe level, with the rising prevalence of the fitness industry on social media, and the boom of easy-access “elite” fitness clubs such as Crossfit and Strongman, there has been a demand to bring fitness back to the “basics.” A treadmill that would more accurately simulate “natural” running scenarios would fit (yes, that’s a pun 😉 ) right into the emerging economic demand for fitness.
Connecting the moving belt to a feedback loop that tracks the runners distance is actually quite ingenious. Rate equals distance over time is one of the simplest relationships learned in elementary physics. And current treadmills always simply manipulate the speed of the belt in order to manipulate the speed of the runner. But, rather than manipulating the the speed, you can now manipulate distance, which will directly affect speed! I am wondering if there is any way that the base of the treadmill could use the runner’s weight and position to determine his or her distance and, accordingly, adjust speed. However, compared to my previous suggestion, it would seem that the use of sonar would actually minimize the number of disturbances that would need to be accounted for. Other than physical damage to the sonar system, and potential items (rarely) falling in the way of the sonar signal, I can’t seem to identify any other disturbances. But what if we consider using the distance the runner is from the front of the treadmill as the control, rather than the distance from the back. I feel like implanting the sonar tracker in front of the runner would minimize the number of disturbances that could potentially get in the way of the signal.
I’m quite conflicted about the type of controller to use in this system. PID seems most logical, but derivative control would be incredibly unstable in this environment (there’s a ton of noise interrupting the sonar signal, and a ton of sustained error to account for). However, derivative action, and its ability to quickly respond to sudden changes, would be invaluable when responding to continual changes in runners’ speed. I wonder if there is a way you could enable/disable derivative control for start-up/shut-down and tripping/stumbling scenarios… Clearly proportional control is most important, so the system can directly respond to changes in a runner’s distance/speed. And integral control would be useful to account for patterned changes in speed. So while PID is the ideal controller to be used, it would be interesting to see if/when individual parts of the control system could be disabled/enabled.
You all did an awesome job analyzing your system thus far. I’m so excited to see how this develops!!
An adaptive treadmill such as the one described in your would be awesome for runners of all kinds. When it comes to running, I much prefer to run outdoors. This is mostly because I like being able to change my pace at a moment’s notice – usually because I’m really out of shape. But like many people, I only like running outdoors when the weather is perfect. I also am a seasonal allergy sufferer, so some days, running outside is just not an option. This self-regulating treadmill would be a god-send for people who don’t want to be bound by the speed of a treadmill but also prefer to spend their time indoors. I can absolutely see myself, and many others, using this product as it brings the best of both worlds together.
The idea to control the distance from the end of the treadmill to the runner is a great one, as it doesn’t place the sensor in the bed of the treadmill. Keeping the sensor external to the treadmill keeps it out of harm’s way. What is very interesting about this application is that, in theory, this could be sold as an accessory for many treadmills. The authors of this blog correctly chose the controlled and manipulated values. This application controls the distance between the sensor and the runner by manipulating the speed of the treadmill. This blog post also hit all of the disturbance variables as well. Something could come between the sensor and the runner, or the runner could stumble/fall. Either of these would cause an unwanted change in the treadmill speed. One possible downfall of this application would be a quick start or stop. It may not be possible for the treadmill to speed up or slow down quick enough during a runner’s quick stop or start. This could be fixed by choosing controller parameters that eliminate this problem.
It is hard to say what kind of controller would be best suited for this application. It almost seems that we would benefit from having two different controllers for different parts of the run. If a runner prefers to start and stop their run quickly, without a gradual speed-up/down, then a controller with derivative control ma be necessary due to its quick response. When sustaining a speed, derivative control may not be ideal, as a disturbance would cause a drastic, quick change in the treadmill speed. This could scare the runner and cause them to fall and possibly hurt themselves. This causes lawsuits, which are no good. In this situation, a slower controller reaction may be favored, but this will only work if runners gradually reduce or increase their speed. Because of these different needs at different times, this control scheme may be very hard to implement. This could explain why it has not been successfully brought to consumer treadmills. I would love to see where this project goes and to see how this application can be perfected!
I think this application would be very helpful, I think one of the worst parts of a treadmill is feeling like I can’t slow down or I need to jump off. Also, having to reach forward and push a button to change the speed after I have gotten into a rhythm is really awful. I have often thought of having a voice controlled system, but even then, trying to talk while running can be annoying as well. After reading this article, I believe this would solve many of my problems. This would be great for large gyms and for domestic use for the avid runner.
The controlled variable seems exactly right, but I don’t know how accurate it would be to measure the position of a body based on their backs. What if a kid is using it and is much shorter then say if a 6’6” adult was using it, would the sonar sensor be able to adjust for that height difference and still be able to measure the distance from the back of the treadmill to the center of their backs? This is something that you might want to look into, my immediate thought without too much pondering, would be to measure the points of contact of the feet. If they get very close to the back of the treadmill, then the controller could slow the belt speed down.
The manipulated variable here would be the speed of the treadmill which would very directly affect the position of the runner. I think it would be especially difficult to account for all possible disturbances. If someone would stumble, or fall, they will always experience this action in different ways, sometimes they will fall backwards, sometimes forwards, and sometimes will fall off sideways. To account for all of these would involve a very specific kind of controller. That is why I think measuring the position of the back would not be a good idea, if they would fall forward, it would appear that they would be running faster, and then the treadmill would increase speed making the fall worse for the individual. Measuring the position of the feet based on sensors measuring the impact points under the feet might be an easier way to do this since their feet will very rarely move towards the front if the runner would fall. One issue I can see with this is if in the process of falling they try to catch themselves and take a very large step forwards or backwards.
I agree that a feedback loop will be best in this application because of the number of disturbances that it would be impossible to measure. I think that a PID controller would be best. Just as my colleague, Sara Mikovic, mentioned in a previous statement, there will be a lot of noise in this system, but the importance of being able to have a quick response to sudden changes is important as this would more accurately replicate a real life situation where the ground moves by just as fast you are running. Most runners once they get into a rhythm will often keep a very constant pace, this can be seen in marathon runners who have very consistent mile split times throughout the 26.2 miles. In terms of tuning and developing controller parameters, I think that using a Cohen-Coon method will be best because trying to tune while the controller is still on in this application could be dangerous. Therefore, I would stick with an Open Loop method.
I am very excited about the prospects of where this application could go, but I believe that there are still a few bugs that need to be figured out before this is ready for the market. I wish you guys the best when trying to do this!
A self-regulating treadmill would be a great product that could be used to emulate a real outdoor running environment! As somebody who enjoys running outdoors but also sees a benefit to controlling the incline of my run, normal treadmills offer a good opportunity to control the running environment. Nonetheless, it is almost never the case that I am able to maintain the same pace for the duration of a run. A self-regulating treadmill is a product that I would love to use and is something that I believe would be a highly sought-after piece of equipment.
The controlled, manipulated and disturbance variables were detailed clearly and correctly. The control aspect makes sense; the belt speed (manipulated variable) will change based on disturbances in the runner’s velocity (disturbance variable) and will be accounted for via changes in the distance between the sensor and the runner (controlled variable). Although this would certainly add an extra component of complexity to the overall control design, it would be interesting to consider designing a treadmill that could instead vary speed based on the runner’s heart rate. If some constant heart-monitoring device were hooked up to the treadmill, this would provide an interesting alternative methodology in how the treadmill speed could be controlled. For example, if the runner’s heart rate was below a desired value, the belt could speed up to help push the runner along. However, I understand that this is outside of the scope of this proposal.
One aspect of the current design that I would be careful to consider is the length of the treadmill itself. In order to allow for the runner to comfortably speed up or slow down without falling off the treadmill or running too close to the front of it, the belt should be long enough as to allow for the runner to modify the running speed without risk of falling or tripping.
Additionally, in order to perhaps avoid the issue of unexpected disturbances (i.e., a water bottle falling and triggering the sonar sensor), an alternative mechanism could be put in place to estimate how the runner slows down or speeds up over time. As the authors stated, there is often a safety clip attached to a treadmill. If the string attached to this clip were released along a belt internal to the treadmill, this clip could send a signal to the controller depending on how far extended it is from the front of the treadmill. As this release distance decreased when the runner speeds up or increased as the runner slows down, the treadmill belt speed could be automatically adjusted accordingly.
I would posit that, as previous commenters have noted, the desired type of control could depend on the status of a run. A controller with derivative control would be helpful in more quickly responding to changes or allowing for fast speed ups or slow downs during a run. However, derivative control may be too sensitive for a sustained speed. This is because any small disturbance may lead to a change in treadmill speed is more extreme than necessary. Ultimately, it would be up to the designers of this product to take into account the interests of the potential clientele, and what type of control action would be best for the product.