The Pacer

Designers: Collyn Heier, Nicholas Mayne, Varun Gudapati, Zachary Brown

Advisors: Brandi McDaniel, Barbara Tapper

Supervising Professors:  Kevin Caves, Chelsea Salinas

Abstract

Our client, an elementary school student, has a walking disability due to a traumatic brain injury that he sustained early in life. He is easily distracted and speeds up while walking, causing him to lose balance and fall. Previously, his therapist used an auditory metronome to help him keep pace, but it did not give him the freedom to walk alone, nor did it provide corrective feedback to keep him focused on his steps. We built a portable pacing device that produces a reference walking beat and offers voice reminders to slow down whenever the client exceeds the set pace. Through testing, the device was shown to be successful in helping him avoid distractions and walk at a steady pace. We hope that it will grant our client more independence in the future, maximizing convenience for him, his parents, and his teachers.

Introduction/Background

Our client Usain is a 5-year-old elementary school student who has a traumatic brain injury. Traumatic brain injury occurs when an outside force damages the brain, commonly resulting in physical and cognitive disabilities [1]. Usain has leg weakness that affects his gait and a cognitive impairment that affects his impulse control. He becomes easily excited and distracted while he walks. When he sees another person, he runs toward them to give them a hug. As a result, he does not focus on his steps and begins to lose his balance.

At school, Usain’s special education class needs to walk through the halls in an orderly fashion. His disabilities make it difficult for him to control his gait and remain in line with the other students. Usain needs a way to pace his walking to avoid harming himself and others. The school therapist discovered that he can regulate his steps by moving his feet to the beat of a metronome. However, he can still become distracted and ignore the sound, prompting the therapist to intervene.

Devices available on the market might address specific aspects of Usain’s disabilities, but no comprehensive solution exists. Traditional pacers produce loud beeps at fixed intervals [2]. Reminder devices use timer-controlled lights and vibrations to indicate when the user needs to focus [3]. However, a traditional pacer cannot prevent Usain from becoming distracted, and reminder devices cannot accommodate his impulsivity.

Project Goals

The goal of this project is to create a device that will help Usain control his pacing when he walks through the hallways at school. The device must last throughout a seven-hour school day, be portable and durable enough for a five year old to carry, and be remotely controlled by the teacher or therapist. Because other students in the class have cognitive disabilities, the pacing mechanism should not be too disruptive in a special education classroom setting.

Design and Development

Our design has three main components: a metronome beat for pacing, pace adherence sensing with voice feedback, and a wearable case that houses the electronics. The casing clips onto a belt that the client wears around his waist. After placing the device on the client, the therapist can remotely turn on the metronome walking beat, toggle the sound output between the speaker and headphones, and adjust the speed setting. This auditory pacing signal sets a reference for Usain’s steps. If he becomes distracted and speeds up, an accelerometer will detect the increase in speed, and the therapist’s voice will remind him to slow down and refocus. This section describes each of these components individually, and explains how they are integrated into a comprehensive solution to our client’s needs.

Metronome Pacing Signal

To provide a reference for Usain’s walking pace, the device produces a soft beeping sound. The signal is controlled remotely, and can be played through a piezoelectric speaker or through headphones.

Signal Generation and Power

Sound Output OptionsThe device generates a reference walking tempo for our client. The tempo can be adjusted remotely to accommodate the client’s stride in different situations. The metronome signal is generated at 500Hz by an Arduino Nano microcontroller at a default tempo of 90 beats per minute. The microcontroller is driven by a 3.7V, 2500mAh lithium polymer battery and PowerBoost 500 charging circuit, which can power the device throughout a seven-hour school day on a single charge.

The metronome sound can be played out loud through an Adafruit piezoelectric speaker. Alternatively, the user can listen to the pacing signal through headphones, which minimizes disruption in the school hallways. A 2kΩ resistor in the circuitry maintains the volume at a safe level. When the sound is toggled to play through headphones, an LED flashes along with the pacing signal. This shows the therapist that the device is powered on and indicates the current speed setting.

Remote Control

The pacing signal can be operated via an Adafruit RF remote control. The remote has four buttons, as depicted in Figure 2. Button A turns the pacing sound on and off. Button B increases the metronome tempo. Button C toggles the sound output between the headphone jack and the piezospeaker. Button D decreases the metronome tempo.

Pace Adherence Sensing and Feedback

The device measures the client’s walking pace and compares it to the signal being generated. When Usain walks too quickly, recordings of the therapist’s voice will prompt him to slow down.

Pace Adherence Detection

An Adafruit MMA8451 accelerometer is connected to the Arduino Nano. It can measure acceleration in all directions. When the user takes a step, the Arduino program calculates the acceleration magnitude vector and compares it to a threshold. This threshold describes the acceleration magnitude of the client’s typical step, which was determined empirically by walking with the client and plotting the acceleration magnitudes. If the value exceeds the threshold, a step is counted. The elapsed time between steps is used to calculate the user’s walking pace. The Arduino software compares this calculated pace to the pace that has been set by the user, and decides if the user is walking too quickly.

Voice Feedback

A DF Player Mini is connected to the Arduino Nano. The Nano can trigger the DF Player to read an MP3 sound file from a micro SD card and play it through the headphones. During testing sessions, it was found that Usain responds well to the therapist’s instructions. Therefore, if the pace adherence algorithm determines that the user is walking too quickly, a recording of the therapist’s voice reminds him to slow down. A reward message plays after the user maintains the target pace for a certain amount of time.

III. Casing and Belt

The electronics of the device are contained within a 3D printed case (Figure 3). The casing walls are 0.5 inches thick to protect against against drops and falls. The circuit components are soldered into a printed circuit board to prevent wires from disconnecting. A clip on the back of the casing allows it latch onto a belt. A toy Batman utility belt was selected to appeal to Usain’s interest in superheroes. A standard, adjustable web belt is also included so it can continue to be worn as Usain grows. The belts are fastened with three-pronged buckles for ease of setup and removal.

Through the use of a metronome pacing signal, pace adherence sensing, and a durable, child-proof casing, this device allows Usain to walk with an auditory reference pace and receive personalized instructions when he experiences difficulty. The use of a metronome beat emulates a practice called rhythmic auditory stimulation, which is used clinically to treat gait disorders [4]. This, in conjunction with the sensing functionality, provides a comprehensive solution for our client’s walking needs. The device is lightweight and portable, and the casing and adjustable belt can withstand years of use by a child. Furthermore, it is well suited for use in a school setting. The rechargeable battery pack can last throughout a full school day, the durable casing protects the sensitive electronics from rough handling, and headphone compatibility prevents the device from disrupting other students.

Evaluation

The pacer device was evaluated to ensure that it met all design specifications and addressed the project goals. Through testing in lab and client use, we ensured that the system was easy to set up, portable, and durable. Tests are described in-depth in Appendix C. After training, the therapist could place the device on the client in less than 15 seconds. To guarantee durability, the device underwent strength testing in the lab. Portability was evaluated by selecting components so that the system weighed less than 1 pound. For safety, the pacing signal was constrained in the software so that the metronome signal could not be set outside of a reasonable walking pace for the client. The system battery was selected to last throughout a seven hour school day on a single charge. We observed that the RF remote’s range was greater than 10 feet, which is sufficient for use at school. Through lab testing and client observation, we verified that a reminder was generated when the client walks faster than the set pace. It was also important that the therapist found the device useful. We gave her a survey with a 5-point Likert scale to determine her level of satisfaction with the technology. The results showed an overall satisfaction score of 4.75 out of 5. The survey results are detailed in Table 1. Finally, we designed the device to be enjoyable for the client. We included the Batman belt to appeal to his interests, and used a clear acrylic lid so the electronics were visible. We recorded a video of the client receiving the device, and he exclaimed, “That’s cool!” Most importantly, we assessed how well the device met the primary need: improving the client’s pace control. We calculated the percentage of the time that the client was on pace when using the device versus walking unassisted. The client walking with our device was on pace 96% ± 4% of the time (mean ± SD) across five trials. This is a statistically significant improvement (p = 0.0005) over the 57±15% recorded when our client was not using the device.

Discussion & Conclusion

Our device provides a mechanism by which our client can drastically improve the pacing of his steps. The design combines the clinically proven use of an auditory pacing signal with easily interpretable feedback to provide a robust and useful device for our client. The cost to recreate our device is $199.63. It meets all of our project goals by providing a consistent pacing signal, tracking our client’s speed and providing feedback, being non-disruptive in the classroom, having an extensive battery life, and being easily adjustable. Further, it is fully portable for a young school aged user and easy to set up by elementary school staff. Our client appears to like the device, and our client’s therapist is confident in the ability of our device to improve our client’s gate control. Therefore, we are hopeful that the created device will provide a mechanism for long-term improvement in our client’s pacing ability, which will positively impact his mobility at school.

References

  1. NINDS Traumatic Brain Injury Information Page. National Institute of Neurological   Disorders and Stroke. 2016. Retrieved September 20, 2016, from http://www.ninds.nih.gov/disorders/tbi/tbi.htm.
  2. Tempo Trainer Pro. Finis. 2016. Retrieved September 20, 2016, from http://www.finisinc.com/Tempo-Trainer-Pro.
  3. The Task Cueing Timer. Assistive Technology Design Projects: Designing Devices for People with Disabilities. 2012. Retrieved September 20, 2016, from https://sites.duke.edu/atdesign/2012/10/10/the-task-cueing-timer/.
  4. Thaut, M.H., et al. Rhythmic auditory stimulation in gait training for Parkinson’s disease patients. Movement Disorders, vol 11, pp. 193-200, March 1996.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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