DAMIAO DM-J6248P-2EC Motor Instruction Manual

DAMIAO DM-J6248P-2EC Motor User Guide

DAMIAO DM-J6248P-2EC Motor

DAMIAO DM-J6248P-2EC: 97N·m high-performance MIT-compatible brushless servo robotic joint motor. For quadrupeds, humanoids & exoskeletons.

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Safety Precautions

1. Operate the motor strictly within the specified environmental conditions and maximum winding temperature limits. Failure to do so may result in permanent damage.
2. Prevent foreign objects from entering the rotor. Otherwise, abnormal operation may occur.
3. Inspect all components before use. Do not operate the motor if any components are missing, wom, or damaged.
4. Ensure correct wiring and proper, secure motor installation.
5. Do not touch the rotating or energized parts during operation to avoid injury. High torque operation may generate heat. Avoid contact to prevent burns.
6. Do not disassemble the motor. Unauthorized disassembly may affect control accuracy or cause malfunction.

Motor Features

1. Dual encoders provide single-turn absolute position feedback at the output shaft, ensuring position information is retained even after power loss.
2. Integrated motor and driver design offers compact structure with high integration.
3. Supports PC-based configuration, monitoring, and firmware upgrades.
4. Provides real-time feedback of motor Velocity, position, torque, and temperature via CAN bus.
5. Features dual temperature protection mechanisms.
6. Supports trapezoidal acceleration and deceleration profiles in position mode.
7. Supports firmware upgrade via CAN.

Naming Conventions

For example：DM - J4340 X - 2EC VX.X (48V)

Specifications

Please operate the motor within the specifications listed below.

Operating Voltage

The operating voltage range for the driver is 24V to 48V. Hot-swapping is not recommended above 36V. The minimum operating voltage is 20V, and the maximum operating voltage is 65V.

Maximum Phase Current

The maximum phase current of the driver can be obtained from the startup serial output:

The maximum phase current percentage can be limited by setting a percentage in the configuration tool. The default value is 0.8 (i.e., 80% of the measurable maximum current). It is recommended that this value not exceed 98%.

Maximum Rotational Speed

The maximum rotational speed is limited by multiple factors, including the power supply voltage (VBUS), rotor flux linkage (ψf), and gear ratio (GR). An upper limit can typically be calculated using the following formula:

$V_{MAX}(rad/s) = 0.57735 * \frac{V_{BUS}}{N_{pp} \times GR \times \psi_f}(rad/s)$

where VBUS is the supply voltage, Npp is the number of pole pairs, and ψf is the rotor flux linkage.

Torque Constant

The torque constant of the motor can be considered constant within its rated range. With a gearbox, it can be calculated using the following formula:

$K_{t} = 1.5 * N_{pp} * \psi_f * GR * GREF$

Where Npp is the number of pole pairs, ψf is the rotor flux linkage, GR is the gear ratio, and GREF is the gearbox torque transmission coefficient.

Torque–Speed (T–N) Curve

The following curve shows the measured performance at 24 V and an ambient temperature of 25° C:

Packing List

1. Motor (with integrated driver) ×1
2. Power cable (with CAN interface) : XT30(2+2)-F connector, single-ended(100mm)×1
3. Debug serial cable: GH1.25 3-pin cable (reverse-side connector, 300mm) ×1

Interface & Pin Description

Motor Dimensions and Mounting

Please install the motor onto the target equipment according to the motor mounting hole dimensions and layout.

LED Status

Operating Modes

MIT Mode

The MIT mode is compatible with the standard MIT control method, enabling seamless switching while allowing flexible configuration of control limits (P_MAX, V_MAX, T_MAX).

CAN commands are converted into torque values. The torque is then used as the reference for current control. See block diagram below.

Based on the MIT model, various control strategies can be derived. For instance, when kp=0 and kd ≠ 0, a constant rotational speed can be achieved by setting v_des. When kp=0 and kd=0, a torque output is applied directly by setting t_ff (feedforward torque).

Position-Velocity Mode

This mode uses three control loops: position, velocity, and current(torque). The position loop sets the target for the velocity loop. The velocity loop then sets the target for the current loop. See block diagram below.

p_des represents the target position, while v_des limits the maximum absolute velocity during motion.

When tuned using recommended parameters from the configuration tool, this mode provides high accuracy and smooth motion, at the cost of slower response time.

In addition to v_des, acceleration and deceleration can also be configured. If additional oscillations occur, increasing acceleration/deceleration may help stabilize the system.

Velocity Mode

This mode keeps the motor running at the target velocity. See block diagram below.

Force-Position Hybrid Mode

The force-position hybrid control mode is based on position-velocity control, with additional torque adjustment. Allows control of both position and output torque at the same time. See block diagram below.

A current command saturation stage is added after the velocity loop output command. This limits the current loop reference within the specified range.

Mode Switching

Mode switching can be configured via the host computer using the serial port. Simply select the desired mode and click "Write Parameters". After successful configuration using this method, the motor will automatically reset, and the mode will be stored inside the motor driver without being lost after power cycling.

Additionally, mode switching can also be performed via the CAN interface by modifying the content of the mode register. For details, refer to the "Mode Switching" section in the next chapter.

When using the CAN method, the motor will not reset, but the following five variables will be cleared to zero:

1. Position command value
2. Velocity command value
3. Torque command value (MIT mode)
4. kp (MIT mode)
5. kd (MIT mode)

CAN communication

After calibration, parameter identification, and parameter configuration are completed, the motor is ready for operation.

Control is performed using CAN standard frames (STD). The default baud rate is 1 Mbps, which can be modified via commands. Refer to the "CAN Baud Rate" section for details.

Frame Types:

CAN communication is divided into two types:

• Command Frames

Frames received by the driver, used to send control commands to the motor.

• Feedback Frames

Frames transmitted by the driver to the upper-level controller, containing motor status data.

Feedback Mechanism:

Feedback operates in a request-response manner. When the driver receives a CAN frame whose ID matches the configured motor CAN ID:

1. The lower 8 bits are used for validation.
2. The upper 3 bits are ignored.

Once a match is detected, the driver will transmit the current motor status to the CAN bus.

Frame Format:

The command frame format and frame ID vary depending on the selected control mode. The feedback frame format remains the same across all control modes.

CAN Baud Rate Configuration

The CAN baud rate can be configured in two ways:

1. Configuration via Serial Interface,.

The baud rate can be set through the host PC software via the serial interface.

1. Select the desired baud rate.
2. Click "Write Parameters" to apply.

After the setting is successfully written:

3. The motor will automatically reboot.
4. The baud rate will be stored in the driver.
5. The setting will persist after power cycling.
2. Configuration via CAN Interface The baud rate can also be modified via the CAN interface by writing to the corresponding baud rate register. See "CAN Baud Rate" in this chapter for details.

Use this method with caution. It is strongly recommended to configure the baud rate before connecting multiple devices.

Feedback Frame

The feedback frame ID is set via the configuration tool (Master ID), with a default value of 0. It primarily reports the motor position, velocity, and torque with the frame format defined as follows:

Where:

1. ID: Controller ID, using the lower 8 bits of CAN_ID
2. ERR : Status code, with the following meanings

0 – Disabled（Default state after power-on）

1 – Enabled

8 — Over-voltage

9 — Under-voltage

A — Over-current

B — MOSFET over-temperature

C — Motor coil over-temperature

D — Communication loss

E — Overload

3. POS : Motor position
4. VEL : Motor velocity
5. T : Motor torque
6. T_MOS : Average MOSFET temperature on the driver (℃ )
7. T_Rotor : Average motor coil temperature (℃ )

Position, velocity, and torque are are converted from floating-point data to signed fixed-point data using a linear mapping:

1. Position: 16-bit signed fixed-point representation.
2. Velocity: 12-bit signed fixed-point representation.
3. Torque: 12-bit signed fixed-point representation.

See the figures below:

3. Torque Linear Mapping

Control Frame in MIT Mode

• Frame ID: Equals the configured CAN ID
• p_des: Desired position
• v_des: Desired velocity
• Kp: Position proportional gain
• Kd: Position derivative gain
• T_ff: Feedforward torque

All parameter follows the mapping rules described in the previous section. The ranges for p_des, v_des, and t_ff can be configured via the configuration tool. Kp range: [0,500], Kd range: [0,5].

A standard CAN frame contains 8 bytes. In MIT mode, the control command packs Position, Velocity,Kp, Kd, and Torque into these 8 bytes:

• Position: 16 bits (2 bytes)
• Velocity: 12 bits
• Kp: 12 bits
• Kd: 12 bits

MIT commands are transmitted by linearly scaling floating-point values into integer representations. The driver converts the received integers back into floating-point values using the same scaling. Two conversion functions are used: float_to_uint, uint_to_float.

Conversion Method:

The conversion requires predefined minimum and maximum values for each variable, which can be configured on the parameter setting page. Default ranges: KP: 0.0 ~ 500.0, KD: 0.0 ~ 5.0.

Position, velocity, and torque are preset to ±12.566, ±20, and ±120. These values can be adjusted according to the motor specifications. When sending control commands, the scaling ranges must remain consistent with the configured values.

Otherwise, the commands will be scaled incorrectly.

Control Frame in Position-Velocity Mode

• Frame ID: equals the configured CAN ID plus an offset of 0x100.
• p_des: Desired position, float type, little-endian (low byte first, high byte last).
• v_des: Desired velocity, float type, little-endian (low byte first, high byte last).

The CAN ID used to send commands here is 0x100 + ID. The velocity command defines the maximum allowable velocity during operation.

Control Frame in Velocity Mode

• Frame ID: equals the configured CAN ID plus an offset of 0x200.
• v_des: Desired velocity, float type, little-endian (low byte first, high byte last).

The CAN ID used to send commands here is 0x200 + ID.

Control Frame in Force-Position Hybrid Control Mode

• P_des: Desired position, in radians, float type, little-endian (low byte first, high byte last).
• V_des: Velocity limit, in rad/s, scaled by 100, unsigned 16-bit, little-endian (low byte first, high byte last). Valid range: 0-10000. Values exceeding 10000 are capped at 10000, corresponding to an actual velocity limit range of 0-100 rad/s.
• I_des: Torque current limit (per-unit), scaled by 10000, unsigned 16-bit type, little-endian (low byte first, high byte last). Valid range: 0-10000. Values exceeding 10000 are capped at 10000, corresponding to an actual current limit amplitude of 0-1.0.
• Per-unit current: Actual current divided by the maximum phase current.

Enable

After the power-on self-test is completed, the "Enable" command must be sent before control can be performed. The "Enable" frame is a control frame, with the frame ID as described previously. The difference lies in the data field. Regardless of which mode the motor is in, the data definition for "Enable" is the same, as follows:

Disable

The default power-on state of the motor is "Disable." In this state, the three-phase terminal voltages are identical, each being a 50% modulation of the power supply voltage. The "Disable" frame is a control frame, with the frame ID as described above. The data payload is defined as follows:

Set Zero Position

The "Set Zero Position" frame is a control frame. This command sets the current output shaft position as the zero reference and resets the position command value to 0. The frame ID follows the definition above, and the data payload is defined as follows:

Clear Faults

When faults such as overheating, sending a "Clear" can be sent to reset the fault state. The "Clear" frame is a control frame. The frame ID follows the definition above, and the data payload is defined as follows:

Read parameters

RID represents the register address; refer to the "Register Map" section for details in this manual.

Upon successful read, the value of the register is returned. The frame format is as follows:

The data is either a floating-point value or an unsigned integer, occupying 32 bits (4 bytes) in total.

The least significant bit is D4, and the most significant bit is D7. The same convention applies below.

Write parameters

RID is defined as above. Upon successful write, the written value is returned. The frame format is identical to the transmitted frame.

Writing register data takes effect immediately but are not stored; They will be lost upon power-off unless a "Save Parameters" command is issued to store them in internal memory

Save parameters

Upon successful execution, the return frame format is:

Mode Switching

Multiple control modes are supported and can be switched as follows:

The mode can be changed by modifying the mode register (0x0A). During switching, the motor resets all command values to zero, including position, velocity, and torque feed-forward, KP, and KD in MIT mode.

When switching to a position control mode, to avoid impact, it is recommended to first read the precise position (value in register 0x50) and perform the switch when the motor is at zero speed whenever possible.

Mode changes are not saved to flash memory and will be lost after power-off. Upon restart, the motor loads the last mode stored in flash.

CAN Baud Rate Modification

By writing specific value to the baud rate register (address 0x23), the current CAN communication baud rate can be modified. Supported baud rates are listed below:

Baud Rate Switching Behavior:

After a successful update, the driver first transmits feedback using the original baud rate and then switch to communication using the new baud rate.

Baud Rate Handling at Power-Up:

At power-up, the driver determines the communication mode based on the stored baud rate.

• If the stored baud rate exceeds 5Mbps, the baud rate is reset to 1Mbps by default.
• If the baud rate is greater than 1 Mbps (excluding 1 Mbps), the driver operates in CAN FD mode.
• If the baud rate is ≤ 1 Mbps, the driver operates in CAN 2.0B mode.

Register List and Range

Host Computer Guide

DAMIAO DM-J6248P-2EC Motor

DAMIAO DM-J6248P-2EC: 97N·m high-performance MIT-compatible brushless servo robotic joint motor. For quadrupeds, humanoids & exoskeletons.

aifitlab.com

On this page

• DAMIAO DM-J6248P-2EC Motor Instruction Manual
• Safety Precautions
• Motor Features
• Naming Conventions
• Specifications
• Operating Voltage
• Maximum Phase Current
• Maximum Rotational Speed
• Torque Constant
• Torque–Speed (T–N) Curve
• Packing List
• Interface & Pin Description
• Motor Dimensions and Mounting
• LED Status
• Operating Modes
• MIT Mode
• Position-Velocity Mode
• Velocity Mode
• Force-Position Hybrid Mode
• Mode Switching
• CAN communication
• CAN Baud Rate Configuration
• Feedback Frame
• Control Frame in MIT Mode
• Control Frame in Position-Velocity Mode
• Control Frame in Velocity Mode
• Control Frame in Force-Position Hybrid Control Mode
• Enable
• Disable
• Set Zero Position
• Clear Faults
• Read parameters
• Write parameters
• Save parameters
• Mode Switching
• CAN Baud Rate Modification
• Register List and Range
• Host Computer Guide