Regenerative Trailer Braking System
University of California, San Diego
Mechanical and Aerospace Engineering
MAE 156B: Senior Design Project
Embedded Files
Background
Background
Inspired by the need for landscapers to navigate stop-and-go traffic on a daily basis, our sponsor at Vogt ranch thought to make a use for all the energy lost to braking during a long day of driving through stop-and-go traffic.
With the Regenerative Trailer Braking System, we are able to make use of braking energy and reduce the wear on a vehicle's brakes by activating regenerative braking on a trailer as it is being hauled. This allows for the driver to capture the otherwise lost braking energy to charge a portable battery mounted on the trailer for use in charging other devices, or propelling the trailer using the electric motor instead of gasoline.
Overview
Overview
The goal of this project in MAE 156B is to be able to create a regenerative braking system that we can attach to a test trailer and use to generate enough power to fill our battery in a single day of driving.
Our system must also have implemented safety measures in place to allow the system to operate in outdoor conditions and to adapt and respond to prevent battery overcharge and system overheating.
Objectives
Objectives
Create an energy generation system that operates an maximum efficiency for electricity generation.
Design a system that can be adapted to a wide variety of trailer configurations.
Keep the total cost under our budget of $5,000.
Final Design
Final Design
Description of Design Solution
Our design solution consists of a generator connected to the axle of a trailer via gear and chain, which leads to a battery where generated electricity is stored. Our controller allows for the user to select a desired braking strength and to be alerted in the case of any system errors. The assembled trailer has a form fator like the image on the right.
Power System Overview
With a variable voltage coming from the generator as the towing vehicle and trailer decelerate, we had to implement a solution to regulate the voltage to a constant level. A constant voltage leading to the battery is needed to successfully charge the battery and prevent damage to the cells within. Power generated from the motor is sent to the controller, then to the battery. The relay acts to maintain continuity through the circuitry of the controller while braking, and breaks discontinuity when braking is not in use or if an emergency is detected by our separate controller.
Control System Overview
The implementation of a control system is required in order to be able to control the braking strength, detect and communicate errors to the driver, and perform emergency controls such as shutting off the charge system if there is an error. To eliminate the need to have a physical wire between the driver's cabin and the trailer, we chose to use ESP32 microcontroller modules equipped with Bluetooth for the exchange of control information between the front and back of the truck.
For the ease of use, both microcontrollers are powered from the car's battery such that they do not need to be charged. Additionally, the minimal user interface gives the driver the ability to quickly and easily change the braking strength.
With safety also being at the forefront of the design plan, we implemented emergency protocol that can activate in the event of a number of errors that can occur. If any error is detected, the driver will be alerted with an alarm played via the speaker of the cabin-side controller module as a red LED flashes. At the same time, the regenerative brake will deactivate slowly over the course of five seconds before fully disconnecting the circuit via the relay that enables power flow between the generator and battery.
Placement of ESP modules in the regenerative braking system.
Simplified electrical diagram for ESP modules.
Diagram of user interface within the cabin.
Video Overview
Design Performance
Design Performance
Final Presentation
Final Presentation
With benchtop testing we have been able to prove the efficacy of the regenerative braking system for a small scale model, but due to logistical issues with acquiring a motor of the correct specifications for a full-sized trailer model we have been unable to construct a system to effectively brake the trailer at a desired deceleration.
When testing the system on a trailer, the power produced resulted in a current of over 40 amps when the braking was engaged at a speed of 15 mph. This in part occurred due to the mass of the towing vehicle generating a greater torque on the generator axle, and thus current generated. With our motor and controller only being rated for 35 amps, we effectively reduced the potential current through the motor and controller by reducing the mass of our towing vehicle by using an electric bike as our towing vehicle.
Below are the results of testing our braking system with the e-bike as a towing vehicle:
The results above indicate that our regenerative system produces a back force that can be used to decelerate the vehicle, but to little difference when compared to the contact brakes of the bike at low level. Due to the greatly reduced mass of the towing vehicle when compared to the truck, the reduced current also produced less of a braking force to slow down the system.
Poster
Poster
Poster Template (2).pdfExecutive Summary
Executive Summary
Executive Summary.pdfPage updated
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