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SMBus battery (a.k.a. smart battery) enhancement. (#14496)

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* Enhancement: State of health, and max_error value is added. Both shows battery health of SMBUS smart battery.
 * Enhancement: BAT_C_MULT parameter is introduced. This is for high-current capable SMBUS-based battery.
As SMBUS only provides 16-bit for current, it could only be +-32768mA which is about +-32A.
But with proper treatment, it could be extended with little accuracy loss.
This factor can be set for individual battery system with available information.
    * Relative SOC introduced. Proper SMBUS battery should provide percentage of remaining battery
directly. Therefore it does not have to be computed like before.
    * State of Health introduced. Proper SMBUS battery should provide SOH value.
    * Max error: this shows estimation error of BMS.
 * Enhancement: With smart battery, precise estimation of time remaining is provided
with impedance track. It is unit of minute, so 60 seconds multiplied.
Update rate of this is not fast, but very useful.

Co-authored-by: Hyon Lim <lim@uvify.com>
This commit is contained in:
Hyon Lim
2020-03-31 17:28:22 -04:00
committed by GitHub
co-authored by Hyon Lim
parent 39b47e63b5
commit 3bcd8c63f8
5 changed files with 51 additions and 17 deletions
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src/drivers/batt_smbus/batt_smbus.cpp
+32 -16
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@@ -89,6 +89,9 @@ void BATT_SMBUS::RunImpl()
// Read data from sensor.
battery_status_s new_report = {};
// TODO(hyonlim): this driver should support multiple SMBUS going forward.
new_report.id = 1;
// Set time of reading.
new_report.timestamp = now;
@@ -108,13 +111,13 @@ void BATT_SMBUS::RunImpl()
// Read current.
ret |= _interface->read_word(BATT_SMBUS_CURRENT, result);
new_report.current_a = (-1.0f * ((float)(*(int16_t *)&result)) / 1000.0f);
new_report.current_a = (-1.0f * ((float)(*(int16_t *)&result)) / 1000.0f) * _c_mult;
new_report.current_filtered_a = new_report.current_a;
// Read average current.
ret |= _interface->read_word(BATT_SMBUS_AVERAGE_CURRENT, result);
float average_current = (-1.0f * ((float)(*(int16_t *)&result)) / 1000.0f);
float average_current = (-1.0f * ((float)(*(int16_t *)&result)) / 1000.0f) * _c_mult;
new_report.average_current_a = average_current;
@@ -122,23 +125,34 @@ void BATT_SMBUS::RunImpl()
// a battery from cutting off while flying with high current near the end of the packs capacity.
set_undervoltage_protection(average_current);
// Read run time to empty.
// Read run time to empty (minutes).
ret |= _interface->read_word(BATT_SMBUS_RUN_TIME_TO_EMPTY, result);
new_report.run_time_to_empty = result;
// Read average time to empty.
// Read average time to empty (minutes).
ret |= _interface->read_word(BATT_SMBUS_AVERAGE_TIME_TO_EMPTY, result);
new_report.average_time_to_empty = result;
// Read remaining capacity.
ret |= _interface->read_word(BATT_SMBUS_REMAINING_CAPACITY, result);
// Calculate remaining capacity percent with complementary filter.
new_report.remaining = 0.8f * _last_report.remaining + 0.2f * (1.0f - (float)((float)(_batt_capacity - result) /
(float)_batt_capacity));
// Calculate total discharged amount in mah.
new_report.discharged_mah = _batt_capacity - (float)result * _c_mult;
// Calculate total discharged amount.
new_report.discharged_mah = _batt_startup_capacity - result;
// Read Relative SOC.
ret |= _interface->read_word(BATT_SMBUS_RELATIVE_SOC, result);
// Normalize 0.0 to 1.0
new_report.remaining = (float)result / 100.0f;
// Read SOH
// TODO(hyonlim): this value can be used for battery_status.warning mavlink message.
ret |= _interface->read_word(BATT_SMBUS_STATE_OF_HEALTH, result);
new_report.state_of_health = result;
// Read Max Error
ret |= _interface->read_word(BATT_SMBUS_MAX_ERROR, result);
new_report.max_error = result;
// Check if max lifetime voltage delta is greater than allowed.
if (_lifetime_max_delta_cell_voltage > BATT_CELL_VOLTAGE_THRESHOLD_FAILED) {
@@ -304,9 +318,16 @@ int BATT_SMBUS::dataflash_write(uint16_t address, void *data, const unsigned len
int BATT_SMBUS::get_startup_info()
{
int result = 0;
// The name field is 21 characters, add one for null terminator.
const unsigned name_length = 22;
// Read battery threshold params on startup.
param_get(param_find("BAT_CRIT_THR"), &_crit_thr);
param_get(param_find("BAT_LOW_THR"), &_low_thr);
param_get(param_find("BAT_EMERGEN_THR"), &_emergency_thr);
param_get(param_find("BAT_C_MULT"), &_c_mult);
// Try and get battery SBS info.
if (_manufacturer_name == nullptr) {
char man_name[name_length] = {};
@@ -334,9 +355,9 @@ int BATT_SMBUS::get_startup_info()
if (!result) {
_serial_number = serial_num;
_batt_startup_capacity = remaining_cap;
_batt_startup_capacity = (uint16_t)((float)remaining_cap * _c_mult);
_cycle_count = cycle_count;
_batt_capacity = full_cap;
_batt_capacity = (uint16_t)((float)full_cap * _c_mult);
}
if (lifetime_data_flush() == PX4_OK) {
@@ -354,11 +375,6 @@ int BATT_SMBUS::get_startup_info()
PX4_WARN("Failed to flush lifetime data");
}
// Read battery threshold params on startup.
param_get(param_find("BAT_CRIT_THR"), &_crit_thr);
param_get(param_find("BAT_LOW_THR"), &_low_thr);
param_get(param_find("BAT_EMERGEN_THR"), &_emergency_thr);
return result;
}