1

Evaluation of Power Control System for Micro and Nano Satellites

by Hardware-in-the-Loop Simulator

Yuji Sakamoto, Toshinori Kuwahara, et al.

Tohoku University, Japan

16 AUG 2012

Small Satellite Conference

UTAH, US

2

3 Background

• SPRITE-SAT (RISING), Tohoku University 1st satellite

– JAN 2009, launched and started operation

• defects of battery charge and discharge H/W control

→ a lot of efforts for power system evaluation were being devoted after following satellites

4

from catalogue of SANYO Twicell(R)

Charging history

Discharging history

ba

tter

y vo

ltag

e (V

) b

atte

ry v

olt

age

(V)

battery capacity (%)

battery capacity (%)

ba

tter

y te

mp

era

ture

(deg

C)

voltage

temp.

environment 20 degC

environment 20 degC

5

• Charging was not stopped at the full capacity

→ capacity was manually controlled by On/Off of instruments

• because of shade by mast, output from one solar panel was decreased

– charging was decreased, and critical low voltage was occurred

• At present, the telemetry signals are not modulated (0.1W CW signals can be monitored)

→ data handling system is defective (estimated)

6 Objectives

• Using Hardware in the Loop (HIL) simulator, power system is evaluated in system level

• Utilized for developing RISING-2 and RAIKO

→ Solar generation power and bus consuming power are supplied or consumed by external equipment

→ onboard power status is monitored by telemetry data

→ results are compared to software simulator, then the math model is improved

7

8 Size: 50x50x50 cm Mass: 41 kg Orbit: SSO, 628-km alt., launched in 2013

Spec. of RISING-2

Lightning and Sprite CMOS Imager (LSI)

- 1st CMOS (762nm) - 2nd CMOS (740-830nm)

- FOV = 27x27 deg

Wide Field CCD (WFC)

FOV = 134x180deg

High Precision Telescope (HPT) - 5-m resolution telescope with ZPF mirror - 10-cm diameter, 1-m focal length - RGB and Multi-spectrum CCDs incl. of LCTF (liquid crystal tunable filter)

Bolometer Array (BOL)

FOV = 29 deg

around Sendai Sta. (3.3 x 2.5 km)

(C)Google

5m reso. ground photo cumulonimbus clouds Sprite, terrestrial lightning events

9

SCU Satellite Central Unit

ACU Attitude Control Unit

SHU Science Handling Unit

PCU Power Control Unit

10

satellite (EM)

dummy solar power dummy ground station (transmitter and receiver for ground station) ground operation software

System-level electrical test

11

specification documents

Quick-Look software (ground

operation soft)

FPGA coding (VHDL)

CPU coding (C, C++)

Word, Excel

Visual C#

Xilinx ISE

Renesus HEW

development of C&DH system

12

(1)

(2)

(3)

(4)

(5)

(6)

13 OLD ground operation software for 1st satellite SPRITE-SAT

difficult to recognize the status and troubles

14 Specs of power system

• RISING-2

– power generation effi. 27.1% of solar cells

– body mound solar panels

– 8-series and 4-pallarel (18.64V, 452mA) for each panel

, or 8-series and 2-pallarel(18.64V, 226mA), total 5 panels

– 41.1W generation power in no-controlled spin motion

– industrial grade NiMH batteries, 9-series and 1-parallel (discharge 10.8V avg, 3700mAh)

• NiMH battery is safe and few risks

• charging is automatically stopped by monitoring voltage and temperature. the setting parameters can be changed by ground commands

15

solar panel simulator (agilent corp. E4350B)

16

electrical load (KIKUSUI PLZ164WA)

17

A. Satellite (REAL)

Data Handling

Unit

RF

TransmitterPower Control

Unit

Telemetry

ReceiverSolar Panel

(Dummy)

Load

(Dummy)

B. Satellite(Simulator)a. Operation

Software(for REAL)

desktop PC #1

desktop PC #2

SIGNAL

POWER

H/W

S/W

RF

telemetry

b. Operation

Software(for Simulator)

command telemetry

HILS

equipment

18 DEMO

19 Software Simulator

• aspects of Software in the Loop(SILS) simulator

– in the combination of SatSimulator and ground operation software, the estimated status of dummy satellite can be checked

– in addition to real-time mode (125-ms period), the fast mode (speed is up to computer) can be available. the simulations with various conditions can be evaluated quickly

• 1: Orbit & Attitude Simulator

– calculating the orbit and attitude

– updating status of orbit, attitude, solar cells, magnetometer, and so on

20 Software Simulator

• 2: coarse control by onboard computer

– magnetic coils control by update values of solar cells and magnetometers

• 3: calculation in power control unit

– decide the battery charging or discharging mode from the comparison of bus consuming power and solar generation power

– decide the voltage and current of solar panels and batteries from the math models

– adopting the power converting efficiency or power loss (70% is suitable in the first stage)

21

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

BA

T-S

OC

(%

)

time after start of eclipse (min)

Battery State of Charge

MIN = 67.5 %(DOD 32.5 %)

sunshine (35.4 - 97.3 min)eclipse (0 - 35.4 min)

MODE-A0

(0 - 10min)MODE-A0

(75-min)

MODE-A0

(25-60min)

MODE-A4

(60-65min)

MODE-S6

(65-75min)

MODE-A4

(10-15min)

MODE-S6

(15-25min)

REAL0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Po

we

r (W

)

time after start of eclipse (min)

Bus Power & Solar Power (RISING-2)

SIMBus P.MIN 11.90,MAX 34.24 W

Solar P.MAX 58.38 W

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

Po

we

r (W

)

time after start of eclipse (min)

Bus Power & Solar Power (RISING-2)

REALBus P.MIN 12.03,MAX 34.55 W

Solar P.MAX 50.02 W

observation mode of 32-W cosumption are carried out in 15 min each in sunshine and eclipse 12W consuming in other periods

Evaluation Results (bus power, solar power)

Hardware (EM)

Soft. Simulator

35-min eclipse -> 62-min sunshine

22

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

BA

T-S

OC

(%

)

time after start of eclipse (min)

Battery State of Charge

MIN = 67.5 %(DOD 32.5 %)

sunshine (35.4 - 97.3 min)eclipse (0 - 35.4 min)

MODE-A0

(0 - 10min)MODE-A0

(75-min)

MODE-A0

(25-60min)

MODE-A4

(60-65min)

MODE-S6

(65-75min)

MODE-A4

(10-15min)

MODE-S6

(15-25min)

REAL

10

11

12

13

14

0 10 20 30 40 50 60 70 80 90 100

T.C

.BA

T-V

(V

)

time after start of eclipse (min)

Temp. Comp. Battery Voltage (RISING-2)

TERM-V (13.13V)at 85.9 min

MAX = 13.17 VMIN = 11.01 V

REAL

10

11

12

13

14

0 10 20 30 40 50 60 70 80 90 100

T.C

.BA

T-V

(V)

time after start of eclipse (min)

Temp. Comp. Battery Voltage (RISING-2)

TERM-V (13.13V)at 77.5 min

MAX = 13.17 VMIN = 11.65 V

SIM

(Temp. Comp. battery voltage)

Hardware (EM)

Soft. Simulator

23

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

BA

T-S

OC

(%

)

time after start of eclipse (min)

Battery State of Charge

MIN = 67.5 %(DOD 32.5 %)

sunshine (35.4 - 97.3 min)eclipse (0 - 35.4 min)

MODE-A0

(0 - 10min)MODE-A0

(75-min)

MODE-A0

(25-60min)

MODE-A4

(60-65min)

MODE-S6

(65-75min)

MODE-A4

(10-15min)

MODE-S6

(15-25min)

REAL

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

BA

T-S

OC

(%

)

time after start of eclipse (min)

Battery State of Charge (RISING-2)

MIN = 69.8 %(DOD 30.2 %)

sunshine (35.4 - 97.3 min)eclipse (0 - 35.4 min)

MODE-A0

(0 - 10min)MODE-A0(75-min)

MODE-A0(25-60min)

MODE-A4(60-65min)

MODE-S6(65-75min)

MODE-A4(10-15min)

MODE-S6(15-25min)

SIM

(Battery State-of-charge)

Hardware (EM)

Soft. Simulator

24 Cubesat RAIKO

by team of Wakayama Univ. and Tohoku Univ.

2.6-kg 2U size Cubesat Using spin-off technologies from 50-kg micro satellites

Now in International Space Station Will be released in September (planned)

25 Cubesat RAIKO Features 1) by total 3 cameras, the photos of ISS, Earth, and stars are obtained * color wide-view CMOS, color fish-eye CCD, and mono CCD * in 30-min after satellite release to orbit, total 46 photos of ISS are taken * photos can be taken at anywhere in globe by task schedule commands 2) high-rate telemetry communication (38.4kbps nom. to 500kbps max.) * 2.2GHz data transmitter, 13GHz data transmitter and 13GHz beacon transmitter 3) 50-cm rectangle thin film is deployed at 300-km alt. for de-orbit experiment

inside of sat. test phote by fish-eye CCD deployable film

26 Spec of power system

• RAIKO

– solar power generation effi. 29.5 % (from catalogue)

– 2-series and 1-pallarel (4.82V, 438mA) for each panel, total 6 panels (12 cells)

– total 10 panels when 2 paddles are opened

– 3.19W power generation in no-control spin motion when paddle closed, and 4.70W when paddle opened

– batteries are commercial NiMH (eneloop), 8-series and 1-parallel (discharge 9.6V avg, 750mAh)

27

0

5

0 10 20 30 40 50 60 70 80 90 100

Po

we

r (W

)

time after start of eclipse (min)

Bus Power & Solar Power (RAIKO)

Bus P.MIN 0.71,MAX 4.56 W

SIM Solar P.MAX 4.93 W

circle orbit51.6-deg incl.300-km alt.2.0-deg/s spin

75

80

85

90

95

100

0 10 20 30 40 50 60 70 80 90 100

BA

T-S

OC

(%

)

time after start of eclipse (min)

Battery State of Charge (RAIKO)

MIN = 92.6 %(DOD 7.4 %)

sunshine (36.3 - 90.5 min)eclipse (0 - 36.3 min)

MODE-S/B(0 - 59min)

MODE-S/B(67-90.5min)

MODE-COMM

(59-67min)

SIMcircle orbit51.6-deg incl.300-km alt.2.0-deg/s spin

(bus power, solar power)

(SOC)

Soft. Simulator

Soft. Simulator

28 Conclusions

• Using hardware and software simulators, the health of system can be estimated in long time span before and after the launch

– defectives can be found

– long-time evaluation of battery performance

– quick evaluation of power system before and after environmental tests

• After the launch, using software simulator including the improved math model, future power status can be estimated correctly (nominal case, and especially emergency case)