To the End Goal

User's actions diagram

This is the simplified user's diagram, where their actions for the intended product is mapped out

Electronics mapping

This is the main electronics used for the product. Future iterations may have it modified, but as of now this is the expected template required to satisfy what is needed.

Microcontroller

For the project, there is a need to read data from sensors, control motors as well as have an internet connection. In order to do so, the NodeMCU is used.

The NodeMCU is a microcontroller based on the ESP-12E. It can be used similarly to an arduino to read or send data on it pins. Additionally it is capable of a wifi and has the ability to send data to the cloud or even host a web server.

It was chosen as it met the requirements and has a large community that provides resources that aid during programming.

Program

For the project, there is a need to program the NodeMCU. In order to do so, the Arduino IDE is used. Additionally, the library i2cdevlib by jrowberg is used to connect and read data from the mpu-6050.

The Arduino IDE was chosen as it met the requirements and has a large community that provides resources that aid during programming.

The i2cdevlib library was chosen as it was the only library that worked with the NodeMCU properly.

Sensors used

For the project, there is a need to measure the positions of body parts in relation to one another. In order to do so, A rotational sensor, the MPU-6050 is used.

The MPU-6050 combines a 3 axis gyroscope, a 3 axis accelerometer and a motion processing unit to report it orientation.

It was chosen as it fulfilled the requirements while being relatively inexpensive.

However there were issues raised by the sensor. If held vertically, it causes a glitch and skips readings drastically, causing inaccuracy. To counter this, the sensor either must never be in a vertical position or upgraded to a MPU-9250 where the magnetometer allows better accuracy.

Motor Driver

For the project, there is a need to control motors. In order to do so, A motor driver, the L298N is used

The L298N can control 2 motors up to a peak motor current of 3A to be able to withstand stall motor currents. It can handle continuous currents of 2A

It was chosen as it fulfilled our requirements while being relatively inexpensive.

Motors used

For the purpose of the project, there is a need for a high torque low speed motor. The motor used has to be small for more discreet looks in the system. The motor has a torque of 8.1kg/cm, a diameter of 20mm and a length of 30mm. Thus it fits the requirements of the project. The required amount of torque to feel an effect was 5kg/cm (tested by the team).

While testing, the motor alone is too weak to have efficient effects. There is a sensation but it does not fit the criteria required. Thus the motors used are connected together with a spool that allows the opposite side to be used. This allows a stronger pull from the motor while fitting the electrical and mechanical requirements of the project.

Material testing

The team is able to create an air bag from the plastic materials given, and is able to shape it in longitudinal tubes. However, the air tightness of these tubing are hindered by the thickness of the material and the sealing at the nozzle/air tubes.

In future designs, the team will try to find a way to keep the nozzle air tight. But for the current project, the air bag prototype was put aside due to many technical difficulties revolving around it.

After conceptualizing a different approach, the team considered using fishing wire through tubing for pulling the body parts together. Fishing wires are strong and able to withstand even resistance placed by the users. It is light and non-rigid yet strong, that is why fishing wire is chosen.

Lubrication is required inside the tubing as there is a large amount of friction acting with the wires and the tubes, and due to the wires getting bent for tying a knot which creates unevenness.

Tubes are to be held together by a 3D printed tube holder to constrain the distance between each tube and to constrain it to the base of the product.

There is a usage of 3 fishing wire instead of 1 to even out the load and not apply high amounts of torque and stress onto the stitched parts. If high torque acts onto a stitched part, the stitching can come off and destroy the product.

The materials used as the base of the product is neoprene due to it meeting the requirements of the project:

It acts as cushion from the sharp electronic parts
The pressure exerted from the fishing wires is spread out
It can be stitched on
It can withstand the weight of motors and parts on top of it without breaking or tearing apart
It is easily shaped and cut for easier fabrication
Material pricing is reasonable
It is non-conductive and protects the users from potential electronic hazards

However due to its thickness and elasticity, it can be difficult to have an accurate and neat stitch

Base stitching

During the prototyping stage, the design had to be stitched quickly. However, how it looks is not consumer friendly and there is a need for the product to be stitched neatly. After some consultations and recommendations, there is a need to get services from people inside the leather crafting industries. The material that is in use (neoprene) is too thick for regular machines to stitch and so the need for manual stitching. Leather craftsmanship has a special tool which allows straight holes to be punched into the materials for neater stitching and smoother appearance.

After testing with neoprene, it was discovered that it is possible to punch holes into it and glue it down for more constrains during stitching for more accuracy. However, neoprene is elastic and can bend and misshape when stitching, being more difficult for accuracy.

Human template (CAD)

For the ease of fabrication, a template is created on a Computer Aided Design (CAD). This allows the team to place the rough sizing of what they want onto it as a comparison, to aid in the decision making and the design process.

Adjustable configurations

As users have different body proportions, an ergonomic method of adjusting has to be implemented for accuracy of the sensors and effectiveness of the entire system.

A velcro system on the sides of the person allows the sensors to be placed correctly and adjustable.

A belt system allows the bottom sensor to be constraint better and prevent the motor from rolling towards the top.

Buckling issue

Due to the high amount of torque exerted on the neoprene material, it causes a buckling effect which reduces its effectiveness and appeal to the users. Thus a solution of stitching down elastic straps were considered. The material cannot be rigid and should be slightly elastic to allow more range of motions. At the same time, it should counter the effects of the buckling effect.

The elastic straps do work as intended. It would be more effective if the elastic straps were longer and past the motors to allow better control over the area, improving the effectiveness and less buckling effects to be detected.

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