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New EPS Requirements
Legend: - M: Must Have - S: Should Have - C: Could Have - W: Won't have
1.1 Its necessary use a external board to charge the batteries before the flight. [M][I]
1.2 The EPS shall have an external connector to charge the batteries that support 3 A and shall have pins redundancy.The connector shall have 2 pins for ground power and 2 pins for Vcharging_batteries .[M][I][R]
1.3 Its necessary charging safely and using charging methods for lithium-ion batteries.[M][T]
1.4 Charging method for lithium-ion batteries shall have three stage:[M][A][T]
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When batteries voltage are under 5.6 -6 V shall have use "a conditioning" stage. The batteries are charged with a 0.1C current limit until it reach 6V.
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CC stage: The batteries are connected to a current-limited power supply, limited to 0.5C - 0.7C, until the cells voltage reach 8.2V.
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CV stage: When the batteries reach 8.4V. The charger shall acts as a voltage limited power supply. The batteries voltage remain at 8.4V while the charge current drops gradually until charge current is between 0.03C and 0.1C of the labeled capacity.
1.5 The board to charger should have battery conditioning, temperature monitoring, charge termination, charge-status indication, and AutoComp charge-rate compensation with this charger parameters: this table. [C][A]
2.1.1 The energy should stored in two rechargeable lithium-ion batteries connected in series. [S][I][A]
2.1.2 The batteries must be cylindrical of 18650 size.
2.1.3 The batteries shall fixed on a auxiliary board called battery board. [M][I][A]
2.1.4 The batteries shall connected to the EPS PCB in three connections; Batteries positive voltage, batteries negative voltage and Batteries middle connection. The connector shall be a power header, shall support until 6 A and shall have pins redundancy. [C][I][R].
2.2.1 The batteries shall a nominal voltage of 3.78 V for each one (7.56 ± 0.2 V for both)
2.2.2 The batteries shall a minimum capacity of 2850 ± 200mAh.
2.2.3 The batteries shall have a nominal capacity of 2950mAh (1C)
2.2.4. Batteries charging method must be: CC-CV (constant voltage with limited current)
2.2.5 The Power Header must have a maximum charge current of 2950 mA.
2.2.6 The Power Header must have a maximum discharge current of 5900 mA.
2.2.7 The batteries board shall connect two batteries in series and should supply up to 25 Wh.
2.2.8 The EPS shall have a cut-off protection when a battery cell reaches 2.75 V or less.
2.2.9 The batteries shall present a voltage difference of no higher than 25 mV before the series connection.
2.2.10 The operating temperature range of the batteries should be :
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Charge : 0 to 45℃
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Discharge: -20 to 50℃
2.2.11 The system shall have energy levels to provide power to the satellite subsystem according to this level.
2.3.1 The batteries board shall have four holes 3.5mm size to fix EPS board with screws and isolators.
2.3.2 The batteries shall be soldered in the batteries board by a 18650 battery holder.
2.3.3 The battery holder should hold the batteries when have vibration on the satellite defined in the section 2.4.1 of this Handbook.
2.3.4 A mechanical holder shall placed over the batteries and screwed to the board.
3.1.1 The satellite shall have six solar panels (one for each face) as the primary source of energy
3.1.2 The solar panels should have integrated coarse sun sensor, temperature sensor magnetorquer and thermistor.
3.1.3 The solar panels shall connected two-by-two (adjacent) in parallel: -Y with +X, -X with +Z and +Y with -Z.
3.1.4 Solar Panels should connected to EPS board using 4-pin Molex PicoBlade connectors and connected as shown on this table.
3.2.1 Solar panels should be at least 29.8% efficient.
3.2.2 Optimal voltage should be 4.74 ± 0.1 V.
3.2.3 The current at optimal voltage should be 499 mA ± 9 mA.
3.2.5 Solar panels should have the operation temperature between -40ºC and +85ºC.
3.2.6 The EPS shall control the solar panels in order to keep the energy harvested within 95% of the maximum capability of the panel for all irradiance intensities.
3.2.7 Three of six solar panels should have magnetorquers each one will pull a maximum of 100 mA totalizing 300 mA. [W]
3.2.8 EPS shall have an independent circuit to control the step-up converter to charge the batteries from the solar panels in case the microcontroller fails (Requirement 10.2). The frequency of the PWM signal generated should be 500 kHz ± 5% and the duty cycle 58% ± 5%. [W]
3.3.1 The width and the height of each panel cannot exceed 98 mm.
3.3.2 Solar panels shall be fixed in structure using 4 screws per solar panel.
4.1 Should have two kill switches to separate the solar panels and the batteries from the load during preflight and launch.
4.2 Each one of kill switch use P-Channel Mosfet in parallel as a redundancy.
4.3 Kill Switch should be connected to the EPS board using 6-pin Molex PicoBlade connectors and connected as shown on this table.
4.4 The satellite should have a Remove Before Flight.
4.4.1 The RBF pin shall cut all power to the satellite once it is inserted into the satellite.
5.1.1The output voltage should be 3.3 V with a maximum current of 2 A.
5.1.2 This regulators should be always on.
5.1.3 The input voltage shall be between 5.5 V and 8.4 V.
5.1.4 This regulators shall have a system Protected by Over Current Limiting, Over Voltage Protection, and Thermal Shutdown.
5.1.5 This regulators shall be a voltage error amplifier.
5.1.6 The regulators should have a operating junction temperature range of -40ºC and +125ºC.
5.2.1 The output voltage should be 5 V with a maximum current of 3 A.
5.2.2 This regulator should be enabled or disabled by EPS through the pin P1.3.
5.2.3 Should follow this requirements: 5.1.3, 5.1.4, 5.1.5, 5.1.6 and 5.1.7.
5.3.1 The output voltage should be 3.3 V with a maximum current of 1 A.
5.3.2 This regulators should be enabled or disabled by EPS through the pin P1.2.
5.3.3 Should follow this requirements: 5.1.3, 5.1.4, 5.1.5, 5.1.6 and 5.1.7.
5.4.1 The output voltage should be 5 V with a maximum current of 5 A.
5.4.3 Should follow this requirements: 5.1.3, 5.1.4, 5.1.5, 5.1.6 and 5.1.7.
6.1 The system shall have three units, each one for each couple of solar panels.
6.2 The output should be the same for all converters.
6.3 Each boost should have a TrenchFET Power MOSFET, N channel, as the switch and this MOSFET should be controlled by a PWM signal generated by the MCU at a frequency of 500 kHz.
6.4 To redundancy, the PCB could have a timer to generate a fixed PWM for the MPPT circuit.
7.1 The EPS shall have 7 power buses as shown below:
- Main power bus (batteries voltage ± 200 mV/3A);
- EPS/Beacon (3.3 ± 0.2 V/2A);
- PA Transceiver Radio (5.0 ± 0.2 V/5A);
- PA Beacon (5.0 ± 0.2 V/5A);
- Antenna Module (3.3 ± 0.2 V/2A);
- OBDH/Transceiver radio/solar panel sensors (3.3 ± 0.2 V/1A);
- RUSH (5.0 ± 0.200 V/3A).
8.1 Should have a system to control the batteries temperature within ± 2 ºC steady state error from the set point when the satellite temperature is less than the set point.
8.2 EPS shall guarantee that the batteries will operate under appropriate temperature conditions (between 0°C and 45°C ).
8.3 Should have a driver with a PWM frequency of 50 kHz and controlled by MOSFETs and the drivers’ mean output voltage must not differ by more than 5% of the desired value.
8.4 Should have four resistance temperature detectors (RTDs) with 1000 Ohms and the temperature range of -60ºC and +200ºC.
8.5 Should have a 24-bit analog-to-digital (ADC) to convert the voltage to digital and send to MCU via SPI protocol.
8.6 Shall have two heaters and each should be connected to a battery.
8.7 Heaters should be connected to EPS board using 8-pin Header Picoblade connectors and connected as shown on this table
9.1.1 The batteries should be controlled by a chip that measures the parameters of item 9.1.3 and sends them to the EPS-MCU via 1-Wire protocol.
9.1.2 Should have protection against: short-circuits, overvoltage, undervoltage and overcurrent.
9.1.3 The batteries monitoring chip shall measure:
- batteries individual voltage (up to 4.6 ± 0.23 V);
- batteries charging current (up to 5.12 ± 0.256 A);
- batteries discharging current (±5% error);
- batteries average current (up to 5.12 ± 0.256 A);
- batteries accumulated current (±5% error);
- EPS temperature (-128 to 128 ± 2 ºC with ±2°C error);
- number of charge/discharge cycles of the batteries (up to 512 cycles).
9.2.1 EPS Shall have batteries undervoltage protection case the batteries voltage is under 5.4 V ±10 %.
9.2.2 EPS Shall have batteries overcurrent voltage case the batteries is over 3.3 A ±5 %.
9.2.3 EPS shall be able to cut off the power delivering to all subsystems (excepting itself and the beacon transmitter) in case of critical low batteries state of charge scenarios.
10.1 The follow items shown the requirements of the microcontroller:
- Low Power 16-Bit RISC CPU
- A SRAM Memory of 64 + 2 KB
- A Flash Memory of 512 KB
- Ultra-Low-Power Consumption
- Low Supply Voltage Range: 3.6 V to 1.8 V
- Full-Speed Universal Serial Bus
- Four 16-bit timers With 3, 5, or 7 Capture/Compare Registers
- A 12 Bit Analog to Digital Converter (ADC)
- Two 12 Bit Digital to Analog Converters (DACs)
- Six Universal Serial communication Interface (USCIs)
- A Real-Time Clock (RTC) Module With Supply Voltage Backup Switch
- Six-Channel Internal DMA
- Up to 74 I/O pins
- A very compact SMD Tuning Fork external Crystal with a frequency of 32.768 kHz and -40ºC and +125ºC operating temperature.
- A Crystal unit for automotive electronics with a frequency of 32 MHz and -40ºC and +125ºC operating temperature.
- A Chip with low-noise, low-drift, very high precision-voltage reference with a maximum of 3ppm/ºC of temperature drift, and a maximum 0.05% of accuracy to generate 2.5 V reference.
10.2 The EPS microcontroller shall provide PWM signals to control the step-up converter. The period of the signals must be 2 us ± 5%. The duty cycles must not differ from the desired value by more than 5%.
11.1.1 Should use a high-precision, low-voltage, high-side current-sense amplifier with current output proportional to the differential input voltage.
- RSense: 50 mΩ (0.5%)
- Rout: 3.3 kΩ
- Gain: 25uA/mV
11.1.3 Every solar panel current from EPS shall be measured individually by a current sensor, with an error of no more than 1.5%.
11.2.1 Should use a single and dual CMOS operational amplifiers, respectively, with low-voltage, low-power, and rail-to-rail output swing capabilities.
- R1: 93.1 kΩ
- R2: 100 kΩ
11.2.3 Every solar panel pair shall have a voltage adaptation system for measurements with an error of no more than 1.5%.
11.2.4 Every solar panel pair adapted voltage from EPS shall be measured by the EPS microcontroller, with an error of no more than 1.5%.
11.3.1 Should use a high-precision, low-voltage, high-side current-sense amplifier with current output proportional to the differential input voltage.
- RSense: 75 mΩ (0.5%)
- Rout: 4.02 kΩ
- Gain: 25uA/mV
11.4.1 Should use a single and dual CMOS operational amplifiers, respectively, with low-voltage, low-power, and rail-to-rail output swing capabilities.
- R1: 300 kΩ
- R2: 100 kΩ
11.5.1 Should be similar than Boos Output Voltage
11.5.2 The main power bus shall have a voltage adaptation system for measurements with an error of no more than 1.5%.
11.5.3 The main power bus voltage shall be measured by the EPS microcontroller with an error of no more than 1.5%.
12.1.1 The satellite should use a Remove Before Flight using 4-pin Header Picoblade connectors and connected as shown on this table.
P.S.: With flight Model, should Swap the pin 2 by pin 3. So 2 RBF jumpers can be used
12.2.1 The satellite should use a RTD1 using 8-pin Header Picoblade connectors and connected as shown on this table.
12.2.2 The sattelite should use a RTD2 using 8-pin Header Picoblade connectors and connected as shown on this table.
12.3.1 The satellite should use a PC104 connector to connect to other boards and connected as shown on this table.
13.1 The EPS MCU shall read from the internal ADC module, the voltage provided by solar panels.
13.2 This read shall happen every 100 milliseconds.
14.1 The EPS MCU shall read from the internal ADC module, the current provided by solar panels.
14.2 This read shall happen every 100 milliseconds.
15.1 The EPS MCU shall read from the internal ADC module, the temperature provided by the MCU internal temperature sensor
15.2 This read shall happen every 1 second.
16.1 The EPS MCU shall read from internal ADC module, the voltage proportional to the EPS-Beacon regulator output current.
16.2 This read shall happen every 1 second.
17.1 The EPS MCU shall read from internal ADC module, the voltage provided by the Main Bus Voltage.
17.2 This read shall happen every 1 second.
18.1 The EPS MCU shall read from internal ADC module, the voltage provided by the Solar Panels Boosts.
18.2 This read shall happen every 1 second.
19.1 The EPS MCU must be able to activate and deactivate the OBDH regulator through the pin P1.2.
19.2 The EPS MCU must be able to activate and deactivate the payload regulator through the pin P1.3.
20.1 The EPS MCU shall calculate every 1 second, the mean of the voltage of the solar panels, with a sample of 10 values.
20.2 The EPS MCU shall calculate every 1 second, the mean of the solar panels current, with a sample of 10 values.
21.1 The EPS MCU shall have an algorithm to control the power consumption of the satellite on different levels of battery charge.
21.2 The Energy Level Algorithm must have five levels of energy.
When the battery charge is decreasing:
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Level 1: Above 80% of battery charge;
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Level 2: Between 80% and 60% of battery charge;
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Level 3: Between 60% and 40% of battery charge;
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Level 4: Between 40% and 20% of battery charge;
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Level 5: Below 20% of battery charge.
When battery charge is increasing:
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Level 1: Above 85% of battery charge;
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Level 2: Between 85% and 65% of battery charge;
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Level 3: Between 65% and 45% of battery charge;
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Level 4: Between 45% and 25% of battery charge;
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Level 5: Below 25% of battery charge.
21.3 The EPS MCU shall have the following behaviors at each level:
| Level | BTI | GTR | TTI | PE | ROA |
|---|---|---|---|---|---|
| L1 | 10s | on | 60s | on | on |
| L2 | 10s | on | 60s | off | on |
| L3 | 20s | on | 120s | off | on |
| L4 | 30s | on | off | off | on |
| L5 | 30s | off | off | off | off |
- (BTI) Beacon signal Transmission Interval.
- (GTR) Enable/Disable General Telecommands Reception
- (TTI) Transceiver periodic telemetry signal Transmission Interval
- (PE) Enable/Disable Payloads Experiment
- (ROA) Turn on/off Regulators of OBDH, Antenna module
22.1 The EPS MCU shall send a packet of data to Beacon, every 10 seconds
22.2 These data must be packaged from the FSP protocol.
22.3 This packet shall have the following structure:
| Position | Variable |
|---|---|
| 0-1 | Battery 1 Voltage |
| 2-3 | Battery 2 Voltage |
| 4-9 | RTD1 - RTD7 Temperatures |
| 10-11 | Batteries Accumulated Current |
| 12-13 | -Y Panel Current |
| 14-15 | +X Panel Current |
| 16-17 | -X Panel Current |
| 18-19 | +Z Panel Current |
| 20-21 | -Z Panel Current |
| 22-23 | +Y Panel Current |
| 24-25 | -Y/+X Panel Voltage |
| 26-27 | -X/+Z Panel Voltage |
| 28-29 | -Z/+Y Panel Voltage |
| 30 | Energy Level |
23.1 The EPS MCU shall send a packet of data to OBDH, always when the OBDH send a request.
23.2 These data must be packaged from the FSP protocol.
23.3 This packet shall have the following structure:
| Position | Variable | Position | Variable |
|---|---|---|---|
| 0-1 | -Y Panel Current | 28-29 | Batteries Monitor Temperature |
| 2-3 | +X Panel Current | 30-31 | Battery 1 Voltage |
| 4-5 | -X Panel Current | 32-33 | Battery 2 Voltage |
| 6-7 | +Z Panel Current | 34-35 | Batteries Current |
| 8-9 | -Z Panel Current | 36-37 | Batteries Accumulated Current |
| 10-11 | +Y Panel Current | 38 | Protection Register |
| 12-13 | -Y/+X Panel Voltage | 39 | Status Register |
| 14-15 | -X/+Z Panel Voltage | 40 | Cycle Counter |
| 16-17 | -Z/+Y Panel Voltage | 41-42 | Remaining active absolute capacity register |
| 18-19 | Solar Panels Boosts Output Voltage | 43-44 | Remaining standby absolute capacity register |
| 20-21 | Main Power Bus Voltage | 45 | Remaining active relative capacity register |
| 22-23 | Beacon-EPS Current | 46 | Remaining standby relative capacity register |
| 24-25 | MCU Internal Temperature | 47-67 | RTD1 - RTD7 Temperatures |
| 26-27 | Batteries Average Current | 68 | Energy Level |
24.1 The EPS shall be able to control the FloripaSat's batteries temperature within ±2°C steady state error from the set point. Also, EPS shall guarantee that the batteries will operate under appropriate temperature conditions (between 0°C and 45°C ).
24.2 The EPS shall provide PWM signals to control the battery heating system. The period of the PWM signals must be 20 ms ± 1ms and the duty cycles should not differ from the desired value by more than 1%.
25.1 The EPS microcontroller shall provide PWM signals to control the step-up converter. The period of the signals must be 2 us ± 5%. The duty cycles must not differ from the desired value by more than 5%.
25.2 The EPS MCU shall have an algorithm to control the duty cycles of the PWM signal, depending on current and voltage of the solar panels to have the maximum power point.
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Modify the item of: 3.2.8 The EPS shall have a step-up converter to charge the batteries from the solar panels with at least 75% of efficiency; 3.2.9 The step-up converter output shall have a voltage adaptation system for measurements with an error of no more than 1.5%. Defined by the team; 3.2.10 The step-up converter output shall be measured by the EPS microcontroller with an error of no more than 1.5%
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reformulate item 4.2
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4.4 Remove Before Flight
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Complete item 9.1.3 with current of discharging and batteries accumulated.
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Remove some itens from 10.1
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Put the resolution of item 14.1
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Put what kinds of situations EPS enable or disabled OBDH or Payloud modules.
*Modify item 24.3 and explain PI Controler and not PWM.