GOMspace NanoPower P60 ACU 200

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Overview

Function Description
Important Technical Specifications
Usage Features
Maintenance Features

The GomSpace NanoPower P60 ACU-200 is a flexible and modular power supply system designed for use in small satellites, specifically as part of the NanoPower P60 EPS (Electrical Power System). This device serves as an Attitude Control Unit (ACU) within the EPS, managing power input from photovoltaic (PV) arrays and regulating charging for the battery pack.

Function Description:

The P60 ACU-200's primary function is to optimize power generation from up to six input channels, each connected to a photovoltaic converter. It supports two main power point tracking modes: Fixed and Tracking. In Fixed mode, the input voltage for charging the battery is set to a predefined vboost[] value and remains constant unless the battery is fully charged. In Tracking mode, the ACU dynamically regulates the input voltage to maximize power generated by the PV arrays. This regulation is constrained by a max_dv parameter, which limits the voltage change from the initial vboost[] setting. The device also incorporates charging control mechanisms to prevent overcharging, regulating the charging power down when the battery voltage exceeds vbat_max_lo and further reducing it to a minimum if vbat_max_hi is reached. Charging resumes only when the battery voltage drops below vbat_max_lo.

The ACU-200 includes hardware protection circuits, working in conjunction with the P60 Dock, to safeguard the battery. If the battery voltage surpasses a hardware protection high threshold, charging is halted and will not resume until the voltage falls below a hardware protection low threshold. These hardware protection thresholds are non-configurable for security reasons.

The device provides comprehensive telemetry data, including measured input voltage and current for each channel, calculated power, charging voltage (vboost[]), VCC, VBAT, and internal temperatures (temp[]). It also tracks uptime and the number of boots.

Important Technical Specifications:

Input Channels: 6 photovoltaic input channels.
Voltage Range (vboost[]): Lower limit of 4300 mV, upper limit of 27000 mV.
Battery Pack Voltage Support: Compatible with 8V, 16V, and 32V battery packs.
Charging Control Parameters:
- vbat_max_hi: Maximum battery voltage high value (e.g., 8300 mV for 8V, 16600 mV for 16V, 33200 mV for 32V).
- vbat_max_lo: Maximum battery voltage low value (e.g., 8150 mV for 8V, 16300 mV for 16V, 32600 mV for 32V).
Hardware Protection Thresholds (non-configurable):
- 8V Battery Pack: High threshold 8400 mV, Low threshold 7625 mV.
- 16V Battery Pack: High threshold 16800 mV, Low threshold 15250 mV.
- 32V Battery Pack: High threshold 33600 mV, Low threshold 30500 mV.
CSP Address: Default is 2.
Serial Connection: 8 databits, 1 stopbit, no parity at 500000 baud.
Firmware Version: 2.0.2.

Usage Features:

Command Interface (GOSH): The P60 ACU-200 can be operated and debugged via the GomSpace Shell (GOSH) interface, accessible through the FPC Debug connector. This command-line interface allows users to execute commands, view identification information (cmp ident), and manage global settings.
CSP Client API: A client API, implemented in p60acu_client.c and p60acu.h, provides wrapper functions to simplify interaction with the ACU-200 via the Cubesat Space Protocol (CSP). This API handles endian conversion and allows for integration into custom code.
Configuration Parameters: The device features three configuration parameter tables:
- Table 0 (Board Parameters): System-level configurations, normally factory-set (e.g., CSP address, I2C address, CAN bitrate).
- Table 1 (Configuration Parameters): Runtime operational and performance parameters (e.g., MPPT mode, vboost[] values, vbat_max_hi, vbat_max_lo, max_dv).
- Table 2 (Calibration Parameters): Factory-configured calibration parameters for voltage and current measurements (e.g., gain_vcc, gain_vbat, gain_v_in, gain_c_in, offs_c_in).
Telemetry Parameters (Table 4): Provides real-time telemetry data, automatically updated once per second by the housekeeping task.
Parameter Management: Parameters can be listed (param list), modified (param set), and saved permanently (param save) to their respective FRAM file numbers.
Ground Watchdog: An essential safety feature that, if enabled, requires activation at least every 48 hours. If the watchdog is triggered (due to lack of communication), the P60 ACU-200 will revert to its default configuration and perform a reset. The timeout value can be configured from 0 seconds (disabled) to 31536000 seconds (365 days).

Maintenance Features:

ESD Sensitivity: The P60 ACU-200 is an ESD sensitive device, requiring proper handling precautions such as using an ESD mat and wrist strap.
Cleaning: Gloves should be worn to avoid fingerprints on anodized aluminum parts. For cleaning prior to flight, only ESD-safe methods and neutral, non-reactive IPA solvent should be used.
Configuration Management: The device maintains two sets of configurations: a running configuration and a default fallback configuration. The default configuration is stored in locked FRAM sectors and can be restored if the ground watchdog is triggered or manually updated.
FRAM Lock/Unlock: Configuration tables (0, 1, and 2) can be locked or unlocked to prevent accidental modification. Table 0 parameters, however, cannot be unlocked or modified remotely via CSP for security reasons, ensuring the CSP address remains fixed in orbit.
Ground Watchdog Reset: The Ground Watchdog Timer can be reset by sending a dedicated command (0x78 to CSP port P60_PORT_GNDWDT_RESET), which is typically used as a ground communication watchdog.