Servo class¶

class Servo(servoid=None, serial=None)[source]¶

Represent a connected Smart HerkuleX Actuator.

Servo class allows to establish serial connection with servos, access configuration parameters, get sensor feedbacks and send control instructions.

Parameters

servoid (int) – The ID of the servo. If not provided, the Servo instance will broadcast any command to all connected servo.
serial (serial.Serial) – port instance of serial.Serial . If not provided, the last used serial port will be used. If no serial port were used yet, an auto detection will be attempted.

Example

#!/usr/bin/env python

import pyherkulex as hx
import time

# Open the serial port (auto detected) with default baud rate 115200
serial0 = hx.serial()

# Broadcast reboot command to all servos connected to serial0
# and light their LED in white
broadcast_srv = hx.Servo(serial = serial0)
broadcast_srv.reboot()
broadcast_srv.led = hx.LED_WHITE

# Create an instance of servo ID 0x01
# (considering the last used serial port
# as no specific port parameter is provided)
srv1 = hx.Servo(0x01)

# Check first if there is any error status
if srv1.status[0]:
    # Print status and raise an exception
    srv1.print_status()
    raise Exception('Please check your HerkuleX servo error status.')

# Print initial position (in step)
print('Servo 1 initial position: ', srv1.position)

# Get initial angular position (in degree)
angle0 = srv1.angle

# Enable control mode before sending control instructions
srv1.mode = hx.MODE_CONTROL

# Increase angular position of 10 degree
# to be completed in an operating goal time of 2 second
# and light LED in blue
srv1.control_angle(angle0+10.0, 2.0, hx.LED_BLUE)

# Wait for control instruction to be completed
time.sleep(2.0)

# Print current position (in step)
print('Servo 1 current position: ', srv1.position)

# Go back to initial position
# to be reached in an operating goal time of 1.5 second
# and light LED in green
srv1.control_angle(angle0, 1.5, hx.LED_GREEN)

# Wait for control instruction to be completed
time.sleep(1.5)

# Switch off LED of servo 1
srv1.led = hx.LED_OFF

Servo class members ¶

Class constants

MODEL

VERSION

POSITION_RESOLUTION_DEGREE

POSITION_MAX

SPEED_INPUT_RESOLUTION_STEP

SPEED_OUTPUT_RESOLUTION_STEP

SPEED_INPUT_RESOLUTION_DEGREE

SPEED_OUTPUT_RESOLUTION_DEGREE

GOAL_SPEED_RESOLUTION_STEP

GOAL_SPEED_RESOLUTION_DEGREE

Configuration methods

Configuration parameters

`status`
`baudrate`
`id`	`id_eeprom`
`led`
`ack_policy`	`ack_policy_eeprom`
`voltage_alarm_led_policy`	`voltage_alarm_led_policy_eeprom`
`position_alarm_led_policy`	`position_alarm_led_policy_eeprom`
`packet_alarm_led_policy`	`packet_alarm_led_policy_eeprom`
`overload_alarm_led_policy`	`overload_alarm_led_policy_eeprom`
`driver_alarm_led_policy`	`driver_alarm_led_policy_eeprom`
`register_alarm_led_policy`	`register_alarm_led_policy_eeprom`
`voltage_mode_free_policy`	`voltage_mode_free_policy_eeprom`
`position_mode_free_policy`	`position_mode_free_policy_eeprom`
`packet_mode_free_policy`	`packet_mode_free_policy_eeprom`
`overload_mode_free_policy`	`overload_mode_free_policy_eeprom`
`driver_mode_free_policy`	`driver_mode_free_policy_eeprom`
`register_mode_free_policy`	`register_mode_free_policy_eeprom`
`max_temperature`	`max_temperature_eeprom`
`min_voltage`	`min_voltage_eeprom`
`max_voltage`	`max_voltage_eeprom`
`alarm_led_period`	`alarm_led_period_eeprom`
`fault_check_period`	`fault_check_period_eeprom`
`packet_garbage_check_period`	`packet_garbage_check_period_eeprom`

Control parameters

`acceleration_ratio`	`acceleration_ratio_eeprom`
`max_acceleration_time`	`max_acceleration_time_eeprom`
`dead_zone`	`dead_zone_eeprom`
`saturator_offset`	`saturator_offset_eeprom`
`saturator_slope`	`saturator_slope_eeprom`
`pwm_offset`	`pwm_offset_eeprom`
`pwm_min`	`pwm_min_eeprom`
`pwm_max`	`pwm_max_eeprom`
`pwm_overload_threshold`	`pwm_overload_threshold_eeprom`
`min_position`	`min_position_eeprom`
`max_position`	`max_position_eeprom`
`position_gain_p`	`position_gain_p_eeprom`
`position_gain_i`	`position_gain_i_eeprom`
`position_gain_d`	`position_gain_d_eeprom`
`feedforward_gain_1`	`feedforward_gain_1_eeprom`
`feedforward_gain_2`	`feedforward_gain_2_eeprom`
`velocity_gain_p`	`velocity_gain_p_eeprom`
`velocity_gain_i`	`velocity_gain_i_eeprom`
`stop_detection_period`	`stop_detection_period_eeprom`
`overload_detection_period`	`overload_detection_period_eeprom`
`stop_threshold`	`stop_threshold_eeprom`
`inposition_margin`	`inposition_margin_eeprom`
`calibration_difference`	`calibration_difference_eeprom`
`mode`

Control sensors

absolute_raw_angle

absolute_goal_position

absolute_goal_angle

absolute_intermediate_goal_position

absolute_intermediate_goal_angle

intermediate_native_goal_speed

intermediate_absolute_goal_speed

intermediate_angular_goal_speed

Class constants ¶

class Servo[source]¶

MODEL¶: HerkuleX servo model value (int) corresponding to the model number (e.g. 201 corresponds to DRS-0201)

VERSION¶: HerkuleX servo firmware version (int)

POSITION_RESOLUTION_DEGREE¶: HerkuleX servo angular position resolution in degree/step (float)

POSITION_MAX¶: HerkuleX servo maximum supported operating position in step (int)

SPEED_INPUT_RESOLUTION_STEP¶: HerkuleX servo absolute speed input resolution in step/second (float)

SPEED_OUTPUT_RESOLUTION_STEP¶: HerkuleX servo absolute speed output resolution in step/second (float)

SPEED_INPUT_RESOLUTION_DEGREE¶: HerkuleX servo angular speed input resolution in degree/second (float)

SPEED_OUTPUT_RESOLUTION_DEGREE¶: HerkuleX servo angular speed output resolution in degree/second (float)

GOAL_SPEED_RESOLUTION_STEP¶: HerkuleX servo absolute goal speed resolution in step/second (float)

GOAL_SPEED_RESOLUTION_DEGREE¶: HerkuleX servo angular goal speed resolution in degree/second (float)

Configuration methods ¶

class Servo[source]¶

reset = <function Servo.reset>[source]¶

reboot = <function Servo.reboot>[source]¶

clear_status = <function Servo.clear_status>[source]¶

print_status = <function Servo.print_status>[source]¶

Configuration parameters ¶

class Servo[source]¶

status¶

Getter: Get status
Setter: Manually set status
Type: tuple of two int values (error status code, detailed status code)

baudrate¶

Getter: Get baud rate in bps
Setter: Set baud rate in bps (save it in EEPROM)
Type: int among the values supported by the HerkuleX servo model

id¶

Getter: Get servo ID
Setter: Set servo ID
Type: int from 0 to 254 (0xFE), with 254 corresponding to broadcast ID.

id_eeprom¶

Getter: Get saved ID from EEPROM
Setter: Save ID in EEPROM
Type: int

led¶

Getter: Get LED color
Setter: Set LED color
Type: int

Supported values are given as LED color constants.

ack_policy¶

Getter: Get acknowledgment policy
Setter: Set acknowledgment policy
Type: int

Three acknowlegement policy values are supported:

ACK_MUTE: With this policy, servo will not reply to any request except status requests.
ACK_READ: With this policy, servo will only reply to read (getter) and status requests.
ACK_ALL: With this policy, servo will reply to all requests.

ack_policy_eeprom¶

Getter: Get saved acknowledgment policy from EEPROM
Setter: Save acknowledgment policy in EEPROM
Type: int

voltage_alarm_led_policy¶

Getter: Get voltage alarm led policy
Setter: Set voltage alarm led policy
Type: bool

voltage_alarm_led_policy_eeprom¶

Getter: Get saved voltage alarm led policy from EEPROM
Setter: Save voltage alarm led policy in EEPROM
Type: bool

position_alarm_led_policy¶

Getter: Get position alarm led policy
Setter: Set position alarm led policy
Type: bool

position_alarm_led_policy_eeprom¶

Getter: Get saved position alarm led policy from EEPROM
Setter: Save position alarm led policy in EEPROM
Type: bool

packet_alarm_led_policy¶

Getter: Get packet alarm led policy
Setter: Set packet alarm led policy
Type: bool

packet_alarm_led_policy_eeprom¶

Getter: Get saved packet alarm led policy from EEPROM
Setter: Save packet alarm led policy in EEPROM
Type: bool

overload_alarm_led_policy¶

Getter: Get overload alarm led policy
Setter: Set overload alarm led policy
Type: bool

overload_alarm_led_policy_eeprom¶

Getter: Get saved overload alarm led policy from EEPROM
Setter: Save overload alarm led policy in EEPROM
Type: bool

driver_alarm_led_policy¶

Getter: Get driver alarm led policy
Setter: Set driver alarm led policy
Type: bool

driver_alarm_led_policy_eeprom¶

Getter: Get saved driver alarm led policy from EEPROM
Setter: Save driver alarm led policy in EEPROM
Type: bool

register_alarm_led_policy¶

Getter: Get register alarm led policy
Setter: Set register alarm led policy
Type: bool

register_alarm_led_policy_eeprom¶

Getter: Get saved register alarm led policy from EEPROM
Setter: Save register alarm led policy in EEPROM
Type: bool

voltage_mode_free_policy¶

Getter: Get voltage mode free policy
Setter: Set voltage mode free policy
Type: bool

voltage_mode_free_policy_eeprom¶

Getter: Get saved voltage mode free policy from EEPROM
Setter: Save voltage mode free policy in EEPROM
Type: bool

position_mode_free_policy¶

Getter: Get position mode free policy
Setter: Set position mode free policy
Type: bool

position_mode_free_policy_eeprom¶

Getter: Get saved position mode free policy from EEPROM
Setter: Save position mode free policy in EEPROM
Type: bool

packet_mode_free_policy¶

Getter: Get packet mode free policy
Setter: Set packet mode free policy
Type: bool

packet_mode_free_policy_eeprom¶

Getter: Get saved packet mode free policy from EEPROM
Setter: Save packet mode free policy in EEPROM
Type: bool

overload_mode_free_policy¶

Getter: Get overload mode free policy
Setter: Set overload mode free policy
Type: bool

overload_mode_free_policy_eeprom¶

Getter: Get saved overload mode free policy from EEPROM
Setter: Save overload mode free policy in EEPROM
Type: bool

driver_mode_free_policy¶

Getter: Get driver mode free policy
Setter: Set driver mode free policy
Type: bool

driver_mode_free_policy_eeprom¶

Getter: Get saved driver mode free policy from EEPROM
Setter: Save driver mode free policy in EEPROM
Type: bool

register_mode_free_policy¶

Getter: Get register mode free policy
Setter: Set register mode free policy
Type: bool

register_mode_free_policy_eeprom¶

Getter: Get saved register mode free policy from EEPROM
Setter: Save register mode free policy in EEPROM
Type: bool

max_temperature¶

Getter: Get maximum allowed temperature (in degree Celsius)
Setter: Set maximum allowed temperature (in degree Celsius)
Type: float

max_temperature_eeprom¶

Getter: Get saved maximum allowed temperature (in degree Celsius) from EEPROM
Setter: Save maximum allowed temperature (in degree Celsius) in EEPROM
Type: float

min_voltage¶

Getter: Get minimum operating voltage (in volt)
Setter: Set minimum operating voltage (in volt)
Type: float

min_voltage_eeprom¶

Getter: Get saved minimum operating voltage (in volt) from EEPROM
Setter: Save minimum operating voltage (in volt) in EEPROM
Type: float

max_voltage¶

Getter: Get maximum operating voltage (in volt)
Setter: Set maximum operating voltage (in volt)
Type: float

max_voltage_eeprom¶

Getter: Get saved maximum operating voltage (in volt) from EEPROM
Setter: Save maximum operating voltage (in volt) in EEPROM
Type: float

alarm_led_period¶

Getter: Get blink period of alarm LED
Setter: Set blink period of alarm LED
Type: float

alarm_led_period_eeprom¶

Getter: Get saved blink period of alarm LED from EEPROM
Setter: Save blink period of alarm LED in EEPROM
Type: float

fault_check_period¶

Getter: Get fault check period for temperature and input voltage
Setter: Set fault check period for temperature and input voltage
Type: float

fault_check_period_eeprom¶

Getter: Get saved fault check period for temperature and input voltage from EEPROM
Setter: Save fault check period for temperature and input voltage in EEPROM
Type: float

packet_garbage_check_period¶

Getter: Get packet garbage check period
Setter: Set packet garbage check period
Type: float

packet_garbage_check_period_eeprom¶

Getter: Get saved packet garbage check period from EEPROM
Setter: Save packet garbage check period in EEPROM
Type: float

Control parameters ¶

class Servo[source]¶

acceleration_ratio¶

Getter: Get acceleration ratio
Setter: Set acceleration ratio
Type: float from 0 (rectangle speed profile) to 0.5 (triangle speed profile)

acceleration_ratio_eeprom¶

Getter: Get saved acceleration ratio from EEPROM
Setter: Save acceleration_ratio in EEPROM
Type: float from 0 (rectangle speed profile) to 0.5 (triangle speed profile)

max_acceleration_time¶

Getter: Get max acceleration time
Setter: Set max acceleration time
Type: float

max_acceleration_time_eeprom¶

Getter: Get saved max acceleration time from EEPROM
Setter: Save max acceleration time in EEPROM
Type: float

dead_zone¶

Getter: Get dead zone
Setter: Set dead zone
Type: int

The dead zone value corresponds to the permitted difference (in step) between goal position and actual position.

If the difference (error) is less than the dead zone value, servo assumes it has reached the goal position and stops.

dead_zone_eeprom¶

Getter: Get saved dead zone from EEPROM
Setter: Save dead zone in EEPROM
Type: int

saturator_offset¶

Getter: Get saturator offset
Setter: Set saturator offset
Type: int

Saturator offset corresponds to the PWM prescribed value when the servo reaches the dead zone boundary.

saturator_offset_eeprom¶

Getter: Get saved saturator offset from EEPROM
Setter: Save saturator offset in EEPROM
Type: int

saturator_slope¶

Getter: Get saturator slop
Setter: Set saturator slop
Type: int

This value corresponds to the slop of the linear transition of the PWM from the saturator offset value to the maximum PWM value versus position.

saturator_slope_eeprom¶

Getter: Get saved saturator slop from EEPROM
Setter: Save saturator slop in EEPROM
Type: int

pwm_offset¶

Getter: Get PWM offset
Setter: Set PWM offset
Type: int

Prescribed PWM will be increased by the amount of the offset. This offset acts similar to a compensator when constant loads are applied on the servo (e.g. from gravity).

pwm_offset_eeprom¶

Getter: Get saved PWM offset from EEPROM
Setter: Save PWM offset in EEPROM
Type: int

pwm_min¶

Getter: Get minimum PWM
Setter: Set minimum PWM
Type: int

Minimum PWM can be used when there is jerky movement due to tight fitting or friction in the servo application system but assigning a minimum PWM value that is too large may lead to unstable system.

pwm_min_eeprom¶

Getter: Get saved minimum PWM from EEPROM
Setter: Save minimum PWM in EEPROM
Type: int

pwm_max¶

Getter: Get maximum PWM
Setter: Set maximum PWM
Type: int

Maximum PWM affects the output maximum torque. Decreasing maximum PWM can also increase battery life.

pwm_max_eeprom¶

Getter: Get saved maximum PWM from EEPROM
Setter: Save maximum PWM in EEPROM
Type: int

pwm_overload_threshold¶

Getter: Get PWM overload threshold
Setter: Set PWM overload threshold
Type: int

Overload activates when external load is greater than PWM overload threshold. Overload never activates when the PWM overload threshold is set to its maximum permitted value.

pwm_overload_threshold_eeprom¶

Getter: Get saved PWM overload threshold from EEPROM
Setter: Save PWM overload threshold in EEPROM
Type: int

min_position¶

Getter: Get min operating position
Setter: Set min operating position
Type: int

min_position_eeprom¶

Getter: Get saved min operating position from EEPROM
Setter: Save min operating position in EEPROM
Type: int

max_position¶

Getter: Get max operating position
Setter: Set max operating position
Type: int

max_position_eeprom¶

Getter: Get saved max operating position from EEPROM
Setter: Save max operating position in EEPROM
Type: int

position_gain_p¶

Getter: Get proportional gain of the position PID
Setter: Set proportional gain of the position PID
Type: float

position_gain_p_eeprom¶

Getter: Get saved proportional gain of the position PID from EEPROM
Setter: Save proportional gain of the position PID in EEPROM
Type: float

position_gain_i¶

Getter: Get integral gain of the position PID
Setter: Set integral gain of the position PID
Type: float

position_gain_i_eeprom¶

Getter: Get saved integral gain of the position PID from EEPROM
Setter: Save integral gain of the position PID in EEPROM
Type: float

position_gain_d¶

Getter: Get derivative gain of the position PID
Setter: Set derivative gain of the position PID
Type: float

position_gain_d_eeprom¶

Getter: Get saved derivative gain of the position PID from EEPROM
Setter: Save derivative gain of the position PID in EEPROM
Type: float

feedforward_gain_1¶

Getter: Get position feedforward first gain (Kd)
Setter: Set position feedforward first gain (Kd)
Type: float

feedforward_gain_1_eeprom¶

Getter: Get saved position feedforward first gain (Kd) from EEPROM
Setter: Save position feedforward first gain (Kd) in EEPROM
Type: float

feedforward_gain_2¶

Getter: Get position feedforward second gain (Kdd)
Setter: Set position feedforward second gain (Kdd)
Type: float

feedforward_gain_2_eeprom¶

Getter: Get saved position feedforward second gain (Kdd) from EEPROM
Setter: Save position feedforward second gain (Kdd) in EEPROM
Type: float

velocity_gain_p¶

Getter: Get proportional gain of the velocity PID
Setter: Set proportional gain of the velocity PID
Type: float

Note

This argument is available only with servo models DRS-0402 and DRS-0602.

velocity_gain_p_eeprom¶

Getter: Get saved proportional gain of the velocity PID from EEPROM
Setter: Save proportional gain of the velocity PID in EEPROM
Type: float

Note

This argument is available only with servo models DRS-0402 and DRS-0602.

velocity_gain_i¶

Getter: Get integral gain of the velocity PID
Setter: Set integral gain of the velocity PID
Type: float

Note

This argument is available only with servo models DRS-0402 and DRS-0602.

velocity_gain_i_eeprom¶

Getter: Get saved integral gain of the velocity PID from EEPROM
Setter: Save integral gain of the velocity PID in EEPROM
Type: float

Note

This argument is available only with servo models DRS-0402 and DRS-0602.

stop_detection_period¶

Getter: Get stop detection period
Setter: Set stop detection period
Type: float

Servo stop is confirmed if stoppage lasts for detection period time.

stop_detection_period_eeprom¶

Getter: Get saved stop detection period from EEPROM
Setter: Save stop detection period in EEPROM
Type: float

overload_detection_period¶

Getter: Get overload detection period
Setter: Set overload detection period
Type: float

overload_detection_period_eeprom¶

Getter: Get saved overload detection period from EEPROM
Setter: Save overload detection period in EEPROM
Type: float

stop_threshold¶

Getter: Get stop threshold
Setter: Set stop threshold
Type: float

The servo is seen as not moving (stopped) when the position movement of the servo is less than the stop threshold value. The servo is determined to be stopped if the stoppage lasts longer than the stop detection period.

stop_threshold_eeprom¶

Getter: Get saved stop threshold from EEPROM
Setter: Save stop threshold in EEPROM
Type: float

inposition_margin¶

Getter: Get inposition margin
Setter: Set inposition margin
Type: float

Standard value to determine if the prescribed position has been reached.

inposition_margin_eeprom¶

Getter: Get saved inposition margin from EEPROM
Setter: Save inposition margin in EEPROM
Type: float

calibration_difference¶

Getter: Get calibration difference
Setter: Set calibration difference
Type: float

Used to calibrate neutral point of the calibrated position (calibrated position = absolute position - calibration difference). It is generally used to make adjustments and compensate assembly variations.

calibration_difference_eeprom¶

Getter: Get saved calibration difference from EEPROM
Setter: Save calibration difference in EEPROM
Type: float

mode¶

Getter: Get servo control mode
Setter: Set servo control mode
Type: int

Three control mode values are supported:

MODE_FREE: In this mode, the servo shaft is freely movable. Position control and speed control will not work. Set MODE_CONTROL before that.
MODE_BRAKE: In this mode, servo motion is prevented. Position control and speed control will not work. Set MODE_CONTROL before that.
MODE_CONTROL: In this mode, control instructions are permitted.

Control actions and outputs ¶

class Servo[source]¶

set_absolute_position_origin = <function Servo.set_absolute_position_origin>[source]¶

reset_absolute_position_origin = <function Servo.reset_absolute_position_origin>[source]¶

speed_mode¶

Getter: Get speed control mode state
Type: bool

Servo.mode value is MODE_CONTROL and continuous rotation is in progress if speed mode is True.

operating_time¶

Getter: Get current operating time (max 2.856 second)
Type: float

control_stop = <function Servo.control_stop>[source]¶

position¶

Getter: Get current (calibrated) position
Type: int

control_position = <function Servo.control_position>[source]¶

control_position_increment = <function Servo.control_position_increment>[source]¶

angle¶

Getter: Get current angular (calibrated) position in degree
Type: float

control_angle = <function Servo.control_angle>[source]¶

control_angle_increment = <function Servo.control_angle_increment>[source]¶

native_speed¶

Getter: Get current native speed
Type: int

control_native_speed = <function Servo.control_native_speed>[source]¶

speed¶

Getter: Get current speed in step/sec
Type: float

control_speed = <function Servo.control_speed>[source]¶

angular_speed¶

Getter: Get current angular speed in degree/second
Type: int

control_angular_speed = <function Servo.control_angular_speed>[source]¶

absolute_position¶

Getter: Get current absolute position
Type: int

absolute_angle¶

Getter: Get current absolute angle
Type: float

absolute_raw_position¶

Getter: Get current absolute raw position (from potentiometer)
Type: int

Note

This argument is available only with servo models DRS-0402 and DRS-0602.

Control sensors ¶

class Servo[source]¶

absolute_raw_angle¶

Getter: Get current absolute raw angle in degree (from potentiometer)
Type: float

Note

This argument is available only with servo models DRS-0402 and DRS-0602.

absolute_goal_position¶

Getter: Get current absolute goal position
Type: int

absolute_goal_angle¶

Getter: Get current absolute goal angle
Type: float

absolute_intermediate_goal_position¶

Getter: Get current absolute intermediate goal position
Type: int

absolute_intermediate_goal_angle¶

Getter: Get current absolute intermediate goal angle
Type: float

intermediate_native_goal_speed¶

Getter: Get current intermediate native goal speed
Type: int

intermediate_absolute_goal_speed¶

Getter: Get current intermediate absolute goal speed in step/second
Type: float

intermediate_angular_goal_speed¶

Getter: Get current intermediate angular goal speed in degree/second
Type: float

pwm¶

Getter: Get current pulse width modulation value.
Type: int from -1023 to 1023

Tip

PWM can be considered as a torque like quantity.

Other sensors ¶

class Servo[source]¶

voltage¶

Getter: Get voltage
Type: float

temperature¶

Getter: Get temperature in degree Celsius
Type: float