SunRover Robot – Solar Power System Ready to Test

Summary

The SunRover solar power power system is ready to be taken out to see first light of the sun.  We have already tested it under a bright light.  We have made some significant changes in the Track Motor subsystem that are talked about below.

What is SunRover?

SunRover is a tracked solar powered robot designed to move around and explore the area while sending back reports, tracking weather, managing a power budget tightly and providing a platform for testing new sensors and equipment as they become available.

The Block Diagram

The major subsystems are shown to the right.   It takes a lot of thought to put together a good block diagram.  You make a lot of design decisions that might be difficult to change later in the design.   Here is a list of the major system decisions:

• – Use a prebuilt Track and Motor controller system
• – Solar Powered system
• – Solar Panels will be shifted from one subsystem to another according to demand and task set
• – Two major computers:  Raspberry Pi 2 for higher levels of control and an Arduino for power management and turning devices and sensors on and off
• – Dual WiFi communication Paths
• – SunRover control panels using RasPiConnect [ www.milocreek.com]

Motor Power Subsystem Restructure

We designed the Motor Power system to stack and unstack three 3.7V LiPo batteries, unstacked – to charge with the SunAirPlus solar

power controller and stacked to run the motors through a TRex controller using Quad Power Management Boards as in the figure to the right.   The system worked perfectly.   It allowed us to put the batteries in parallel and then stack them for running the SunRover motors.   However, when integrating the solar power charging SunAirPlus boards into the system, we found a problem.  The problem was that there were too many gate and diode voltage drops from the solar power charger to the batteries to effectively charge the batteries.   This was something we should have caught earlier in the design.  So, to fix this we replaced the battery stacking circuitry with a DROK 3.5V – 30V Adjustable DC Boost converter.  We programmed the DROK to go from 3.7V to 30V, hooked it up and it was ready to go.  We hooked the TRex Controller power input to the Output of the DROK.  We then paralleled the fully charged 3 LiPo cells (important to have all the batteries at approximately the same voltage to hook them together!) and connected them to the input.  Works like a champ.   We are using the Quad Power Management board next to the DROK to switch the power to the motors on and off to save current and as an emergency cutoff if SunRover starts heading south.  Note the nice Blue cycling input / output voltage display above.   This can be turned off to save current.   The motors run perfectly with no noise problems through this board.

Solar Power System

The solar power system consists of 6 Voltaic Systems solar panels, three SunAirPlus solar power controllers (for three separate power

systems!), a solar panel multiplexer based on Quad Power Management boards and an low power Arduino Based Management system to control the multiplexer and to switch the other computers on and off appropriately.  The system has been tested indoors with an external power supply simulating the solar cells and also with a bright light on the panels to make sure all the wires are connected.

It will be sunny over the next week, so expect actual outdoor driving and solar panel testing soon.