Transcript *Mars* Rover Battery Charger

“Mars” Rover Battery Charger
Nick Italiano, Alex Fordyce, Aaron
Moldenhauer
INTRODUCTION
•Larger project: STELLArS
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Middle school program
Grows interest in STEM fields
Miniature Mars Rover
Virtual Mars atmosphere
•Problem: the rover needs to
recharge!
OBJECTIVES
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Wireless charging
Fast recharge
Cost
Efficiency
Safety
WIRELESS POWER
•Objective: Deliver 48 watts of
power wirelessly
•Solution: Resonantly Coupled
Inductors
•Input Restrictions: None
•Output Goal: 12V, 4A
•Output of Current Design:
-[PENDING]
POWER ELECTRONICS
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Objective: Rectify and convert power
Method: Bridge Rectifier and DC/DC Converter
Input = 12 V + 20% AC
Output = 20 V + 5%, <20 W
Status
CONTROL
• Objective: Charge battery fully and safely
• Solution: Circuit centered around Battery Management IC
• Output Goal: Constant-Current until battery is 8.4 V and then
charge with constant-voltage.
• Current Status
CONCLUSIONS
 Finish constructing recent revisions
 Continue testing
 Work on connecting together
Thank You
Wireless Power Math
In order to get maximum power transmitted, the Q-factor
of the inductor has to be equal to 1/k where k is the
coupling coefficient
We know the load resistance and can approximate the
coupling coefficient. Therefore, we can calculate the
inductance value (for matched Q) using…
We can choose an resonant frequency, and then choose a
capacitance value based on…
1
𝑘= ′
𝑄
𝑅𝑄′
𝐿=
𝜔𝑜
𝐶=
1
𝜔𝑜2 𝐿
Wireless Power Math
Let’s approximate k as 10% coupling between coils
1
1
′
𝑄 = =
= 10
𝑘 0.1
We would like the load to be able to draw up to 4 amps at 12 volts. With these
numbers the highest power equivalent resistor is 3Ω
𝑅𝑄′
3 ∗ 10
𝐿=
=
= 19.1𝜇𝐻
𝜔𝑜
2𝜋 ∗ 250𝑒3
1
1
𝐶= 2 =
= 21.2𝑛𝐹
3
2
−6
2𝜋
∗
250𝑒
∗
19.1𝑒
𝜔𝑜 𝐿
Try to make the primary side identical to the secondary side
Wireless Power Schematic and Plot
Wireless Power Circuit Test
Our 250kHz Inverter Output
Power from Outlet
Wireless Power
Power Systems
(Regulator/Regulator)
Battery Charge
Management
Power to the Battery