Manual Transmission Car Hand Controls

Written by: ACI.engineering

We are a group of three mechanical engineers from San Francisco State University and here we would like to share our senior design project.

The goal of this project is to help paraplegics gain their independence and provide them with a convenient ability to drive cars with manual transmissions if so they choose or due to necessity. We have built a device that operates in conjunction with an already existing hand controls type of device used to drive automatic cars. It operates the clutch pedal through a steering wheel mounted lever a user controls with their hand. Theoretically, this device should be compatible with a wide range of manual cars, however, we only tested it on one. Additionally, it require no permanent modifications to the car, and it is easily installed and removed.

 

You can find out more information by visiting our website:

http://manualcontrols.weebly.com/

How it works

We will use this controls simulation stand to demonstrate how it works outside of a car.

Since the user will only have their two hands to operate all the controls with, they must be able to steer the car, control the clutch, brake and gas, as well as the gear stick. The way we chose to approach this is by having the left hand turn the steering wheel and control the clutch, while the right hand controls the gas, brake and the gear lever. Placing the clutch lever on the steering wheel permits the driver to maintain one hand on the wheel at all times.

With the right hand, the driver controls the gas and brake through a conventional hand controls device that is originally intended for automatic transmission cars. With their left thumb, they operate a spring loaded lever that relates the position of the lever to the position of the clutch. Pushing the clutch pedal are a pair of high speed linear actuators from Firgelli Automation mated to a linear potentiometer that reads their position.

The hand clutch

The 3D printed lever mechanism controls a potentiometer. The signal is fed to a microcontroller which transmits it wirelessly to another microcontroller mounted on the floor. The reason this has to be wireless is because having wires run down from the steering wheel while its turned from lock to lock is probably a bad idea.

Control system

Attached to the mounting board, which is designed to use the two front seat mounting bolts in a car as its anchor points, is the main controller. Receiving the input signal from the potentiometer on the wheel and the position value from the linear potentiometer (which we will get to in a second) mounted to the clutch pedal, the controller uses a PI feedback loop to precisely control the position of the actuators.
The joystick located right under the shifter, which can be mounted anywhere in the car, is a backup controller. In the case of wireless transmission failure, the backup controller provides a reliable, wired, control of the actuators so the driver can pull over to safety and repair the system.
An LED mounted to the shifter cycles between different colors as the actuators extend to provide a visual reference to the pedal's position.

Pedal mount

The actuators are attached to the clutch pedal via custom steel bracket. It is designed to be able to pivot as the angle of the actuators in relation to the face of the pedal changes. Connecting the front of the actuators to the linear potentiometer mounted on top is this blue link.

The actuators

The linear actuators which make all of this possible are supplied by Firgelli Automations.

They are high speed actuators with a 10" stroke, 22 lbs of force, and a travel speed of 9" per second at no load or 4.5" per second at full load. The reason we used two of them in parallel is so that the load is distributed such that they will have enough force to push heavy clutch pedals and be able to operate  further from their full capacity in order to maintain the high rate of extension.

https://www.firgelliauto.com/products/high-speed-actuator

 

Reading their position and allowing the system to operate in a closed loop is the linear potentiometer mounted on top. Also by Firgelli Automations, this potentiometer has 10" of extension and a range of 10 k ohms.

https://www.firgelliauto.com/products/potentiometer

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