P17214: Smart Mountain Bike Suspension
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

In this phase our team worked to do further feasibility testing of the mechanical aspects of the suspension adjustment and to finalize the selection of our electronic parts.

Testing the torque of the Dials on the fox suspension allowed us to select servos with a suitable torque rating and response time. Preliminary modeling of the servo mounts allowed us to verify that there would be no interference with other parts mounted on the bike.

A large amount of time was spent looking into datasheets for the various electronic components to ensure that there were software libraries available that would support the selected devices.

It was critical to finalize the bill of materials at this time as our team was meeting with the Simone Center at the end of this phase to acquire additional funding for suspension products to test the final product with. After meeting with Dr. DeMartino of the Simone Center, a revised budget of $3000 was approved for the development of a prototype device provided members of the project team complete a seminar course in the fall semester.


Feasibility: Prototyping, Analysis, Simulation

Servo Motor Torque Feasibility

To test if the servos that we picked to actuate our suspension would have enough torque we had to measure the torque that was required to turn the dials on the suspension.
Rear Dial Torque Test

Rear Dial Torque Test

The above picture is of the test done to determine the torque that is required to turn the rear dial on the Fox Suspension.
Front Dial Torque Test

Front Dial Torque Test

The above picture is of the test done to determine the torque that is required to turn the front dial on the Fox Suspension.

The servo motors that were ordered had a torque rating of 12 kg-cm. It was determined that the torque required to turn the front dial on the Suspension was .72 kg-cm and the rear dial required .705 kg-cm. This means we have a lot of room to work with if we want to gear the servo at all

Servo Motor Torque Test

Servo Motor Torque Test

The above picture is of a verification test done on the servo. A 2 Kg mass was hung at a distance of 2.5 cm from the center of motor, for a measured torque of 5 Kg-cm. It was verified that the servos that were ordered for the part will work just fine, giving a safety factor of at least 5x, meaning that it should be possible to gear the servos down for increased response speed.

MicroController Selection

After we determined the necessary components at a system level, we wanted to ensure that the selected microcontroller would support all of the devices that we require for the solution. The following chart details the required I/O pins for the peripheral devices.

MicroController Pin Out

MicroController Pin Out

In order to determine which microcontroller would be the best product for our solution, we created a pugh chart to rank the various features of each against the requirements.

MicroController Pugh Chart

MicroController Pugh Chart

The availability of software libraries made the Arduino based option stand far ahead of both the NXP and TI microcontrollers. The easy programming interface and an ARM based design with a floating point unit will ensure that the development time for the software is based solely on the implementation of control theory, and not replicating work previously done to interface with the peripheral devices.

Drawings, Schematics, Flow Charts, Simulations

Preliminary Designs

Servo Dimensions
Servo Dimensions

Servo Dimensions

The Servo dimensions and the suspension diameters are the driving measurements of our designs. Creating mounts that hold the servo in place and keep a solid grip on the shock diameter is crucial.

Power and Micro Controller Housing
Housing Ideas

Housing Ideas

Housing Ideas

Housing Ideas

The desire of the Power and Micro Controller Housing is to save room, reject water and dirt, have useful airflow, and to keep components in place. The location for our case design will be under the top tube of the frame, above the bottle cage mount, and ahead of the drive train. The design includes a water trap, ventilation, and mounts for the battery and microcontroller.

Lidar and Front Shock Servo Mount
Lidar Mount Idea

Lidar Mount Idea

Lidar Mount and Front Mount

Lidar Mount and Front Mount

Lidar Mount Brim Idea

Lidar Mount Brim Idea

The Lidar Mount's design requirements is to have an adjustable angle arm, secure the Lidar, and protect the lens from debris such as dirt or small rocks. The inspiration for the mount came from the GoPro mounts.

The Front Servo Mount's design needs to translate torque to a parallel pin and the geometry of the Shocks housing is not a perfect circle. This requires the mount to wrap around the diameter and then use a ring around the bridge of the fork to securely mount. This system will be using a belt to alternate the Suspension settings

Rear Shock Servo Mount
Rear Servo Mount Idea

Rear Servo Mount Idea

The Rear Servo Mount was designed for prototyping the pulley system for alternating settings. It uses two horseshoe like clamps to grip the static diameter of the shock.

CAD Models

Power and Controller Housing Model
Battery and Micro Controller Housing, Solidworks 2015

Battery and Micro Controller Housing, Solidworks 2015

Front Shock Servo Mount Model
Front Shock Servo Mount Complete Assembly, Solidworks 2015

Front Shock Servo Mount Complete Assembly, Solidworks 2015

Front Shock Servo Mount top view, Solidworks 2015

Front Shock Servo Mount top view, Solidworks 2015

Front Shock Servo Mount exploded view, Solidworks 2015

Front Shock Servo Mount exploded view, Solidworks 2015

Rear Shock Servo Mount Model
Rear Servo Mount Isometric Assembled View, Solidworks 2015

Rear Servo Mount Isometric Assembled View, Solidworks 2015

Rear Servo Mount Exploded View, Solidworks 2015

Rear Servo Mount Exploded View, Solidworks 2015

Lidar Mount Model
Lidar Test Mount Isometric Assembled View, Solidworks 2015

Lidar Test Mount Isometric Assembled View, Solidworks 2015

Bill of Materials (BOM)

The updated Bill of Materials is shown below.
Bill of Materials

Bill of Materials

A link to the live document can be found here

Test Plans

1. Lidar

What needs to be tested? The accuracy and range of the Lidar needs to be tested to determine whether or not it can accurately detect the terrain.

How will it be tested? We will collect data from the Lidar with known distances (2-4 meters) and object heights (3 - 6 inches) in order to determine the Lidar's accuracy.

Materials Needed for Testing:

Criteria for Testing: Verify that the Lidar can collect accurate data from 3 meters away with an error of 5% or less.

Risks:

2. Servo

What needs to be tested? The speed, torque and accuracy of the Servo needs to be tested.

How will it be tested? The servos will be placed on the suspension switches, then by manipulating the servos we will test if the Servos have enough torque to move the suspension switches, along with moving the switches to the correct location. The speed of the Servos moving once given a command through the microcontroller can also be tested.

Materials Needed for Testing:

Criteria for Testing:

Risks:

3. Cadence

What needs to be tested? The Cadence sensor needs to be tested to make sure the pedaling is accurately detected.

How will it be tested? The Cadence sensor will be placed on the bike and tested by pedaling at different rates. This will verify that the sensor is accurately detecting the pedal rate.

Materials Needed for Testing:

Criteria for Testing: Verify that the Cadence sensor is detecting the pedal rate within and accuracy of 5% as verified by a Garmin ANT+ Cadence sensor linked to a cycling computer.

Risks:

4. Accelerometer

What needs to be tested? The accuracy of the Accelerometer needs to be tested.

How will it be tested? The Accelerometer would first be calibrated by mounting it onto the bike and then placing the bike on even ground. This would then be considered the "zero" state for the Accelerometer. Then the bike would be placed on different hills and terrains to determine if the Accelerometer is accurate enough to detect the difference. The ability to detect the bike going up and down hill will also be verified.

Materials Needed for Testing:

Criteria for Testing: Verify that the Accelerometer can detect a difference of at least 30 degrees on varying hills and on different terrains.

Risks:

Design and Flowcharts

An Update to the level 1 system architecture is below

Level 2 System Architecture

Level 2 System Architecture

A first draft of the software flow chart is presented below

Software Flow Diagram

Software Flow Diagram

Risk Assessment

Updated Risk Assessment chart for phase 3.
Updated Risk Chart

Updated Risk Chart

A link to the live document can be found here

Updated Gantt Chart

Gantt Chart as of Week 11

Gantt Chart as of Week 11

Here is a link to the live Gantt Chart

Gantt Chart

Plans for next phase

Individual 3 Week Goals

Each member of the team has mapped out their goals and tasks for the next three week phase of the MSD 1 project. Individual plans are listed below

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