The ROBOTOUS RFT Series is a 6-Axis Force Torque Sensor designed for applications requiring dexterity, safety, and scalability. It measures forces along the X, Y, and Z axes (Fx, Fy, Fz) and torques around these axes (Tx, Ty, Tz).
Function Description:
The RFT Series sensor provides real-time force and torque data, enabling precise control and interaction in robotic systems. It operates by detecting changes in capacitance due to structural deformation, offering a robust and reliable measurement. The sensor supports various communication interfaces, including CAN, RS-232, RS-422, USB (Virtual COM port), and EtherCAT (with an external board or embedded in specific models like RFT80-6A02 and RFT64-6A01).
Important Technical Specifications:
Power Supply:
- Input Voltage: 5V DC
- Max. Power Consumption: 0.5W
- Input Voltage Tolerance: ±10% (Exceeding limits may damage the sensor)
Communication Settings (Default):
- Filtering: Filter OFF
- Data Output Rate: 200Hz
- CAN:
- Receiver ID: 100 (0x64)
- Transmitter ID #1: 1 (0x01)
- Transmitter ID #2: 2 (0x02)
- Compatibility: CAN 2.0 A, B Compatible
- Identifier: Standard Identifier
- Bit Rate: 1Mbps
- Size of Data: 8 Bytes
- UART:
- Baud Rate: 115,200bps
- Stop Bit: 1
- Parity: No
- Flow Control: No
- Data Length: 8 Bits
Packet Structure:
- Command Packet:
- Data Field Size: 8 bytes
- SOP (Start Of Packet): 85 (0x55)
- EOP (End Of Packet): 170 (0xAA)
- Response Packet:
- Data Field Size: 16 bytes
- SOP (Start Of Packet): 85 (0x55)
- EOP (End Of Packet): 170 (0xAA)
Force/Torque Data Conversion:
Raw data from the sensor is a signed 16-bit integer. To convert to actual force and torque values, the raw data is divided by specific Divider (DF) and Divider (DT) values, respectively. These dividers vary by model:
- RFT80-6A02, RFT80-6A01, RFT64-6A01: DF = 50, DT = 1000
- RFT64-SB01, RFT60-HA01, RFT44-SB01, RFT40-SA01: DF = 50, DT = 2000
Overload Status:
The sensor provides an overload status (R13 in response packet) where individual bits (Bit0 to Bit5) indicate if the corresponding force or torque component (Fx, Fy, Fz, Tx, Ty, Tz) exceeds its rated load capacity by more than 20%. A bit set to 1 indicates overload, 0 otherwise.
- Dimensions: Ø 90mm, H 33mm
- Weight: 418g
- Max. Force (Fx, Fy, Fz): 1,000 N
- Max. Torque (Tx, Ty, Tz): 100 Nm
- Resolution (Fx, Fy, Fz): 4 mN
- Resolution (Tx, Ty, Tz): 4 mNm
- Hysteresis (Fx, Fy, Fz): 1%FS
- Hysteresis (Tx, Ty, Tz): 2%FS
- Overload Capacity (Fx, Fy, Fz): 300%
- Overload Capacity (Tx, Ty, Tz): 300%
- Crosstalk: 3%FS
Usage Features:
General Operation:
- Start/Stop Data Output: The sensor remains idle after power-up until the "Start F/T Data Output" command (Command ID = 11(0x0B)) is sent. To stop data output, the "Stop F/T Data Output" command (Command ID = 12(0x0C)) is used.
- Parameter Setting: Parameters can be set either in the idle state or after stopping data output. The sensor can save current parameter settings, which persist after rebooting, except for "Start F/T Data Output," "Stop F/T Data Output," and "Set Bias."
- Setting Bias: The "Set Bias" command (Command ID = 17(0x11)) can be executed while measuring force and torque data to zero out current readings.
- Filtering: The sensor supports filtering, which can be configured using the "Set Filter" command (Command ID = 8(0x08)). Filter types include "No filter" and "1st order low-pass filter" with various cutoff frequencies.
- Data Output Rate: The data output rate can be adjusted using the "Set Data Output Rate" command (Command ID = 15(0x0F)). Allowable rates depend on the communication interface (CAN or UART) and baud rate.
- Communication ID (CAN only): Receiver and Transmitter IDs can be set using the "Set Communication ID" command (Command ID = 4(0x04)). New IDs are applied after a sensor reboot.
- Baud Rate (UART only): The baud rate can be configured using the "Set Baud-rate" command (Command ID = 6(0x06)).
Communication Protocol:
- CAN Interface: The sensor uses CAN 2.0 A, B Compatible protocol with standard identifiers.
- UART Interface: The sensor uses a serial communication protocol with configurable baud rates, 1 stop bit, no parity, and no flow control.
- Shielding: The shield line of the sensor cable is connected to the internal GND, so external grounding is not strictly necessary.
- Terminal Resistor: For CAN and RS-422 interfaces, a 120Ω terminal resistor must be connected for normal operation, as the sensor does not have an internal resistor.
- RS-232: RX from one device connects to TX of the other, and vice-versa.
Sensor Models and Features:
- RFT90-6A01: Ø90mm, High resolution, Temp. compensation
- RFT80-6A02: Ø80mm, High resolution, Temp. compensation
- RFT80-6A01: Ø80mm, High resolution
- RFT64-6A01: Ø64mm, High resolution, Temp. compensation
- RFT64-SB01: Ø64mm, Dust seal
- RFT60-HA01: Ø60mm, Hollow core
- RFT44-SB01: Ø44mm, Dust seal
The product ordering information follows a format like RFT[Sensor Feature]-[Interface Method][Cable Option].
- Sensor Feature: Specifies the model (e.g., RFT64-SB01 for Ø64mm Solid core, Dust seal).
- Interface Method: A (CAN), B (RS-232), C (RS-422), D (USB), E (EtherCAT).
- Cable Option: "" (Default, Shielded, General signal cable, 2 meters), R3 (Shielded, Robot cable, 3 meters), R5 (Shielded, Robot cable, 5 meters).
- Example:
RFT64-SB01-A indicates a ROBOTOUS Force/Torque Sensor with Ø64mm Solid core, Dust seal, and CAN Interface.
Maintenance Features:
Error Codes:
The sensor provides error codes in response packets to indicate issues:
- 1(0x01): Unsupported command.
- 2(0x02): Out of range error, a parameter such as ID, baud-rate, filter setting, etc., is out of the allowable range.
- 3(0x03): Failed to set parameters.
Calibration:
The sensor is designed for reliable performance. While the manual does not explicitly detail user-level calibration procedures, the "Set Bias" command allows for zeroing out current force/torque readings, which can be considered a form of field calibration for current conditions.
Durability:
The RFT Series features high durability and mechanical overload protection. It is designed to withstand forces and torques exceeding its rated capacity by up to 300% (overload capacity).
Environmental Considerations:
The manual warns that sudden changes in temperature and humidity may affect sensor output and cause erratic readings. Users should ensure stable environmental conditions for optimal performance.
Installation:
The manual includes detailed wiring diagrams for various sensor models and communication interfaces, ensuring correct connection to host systems. It emphasizes matching wire colors to correct functions to prevent damage.
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