Torque sensors are commonly used in robot structures. Robot torque sensors are typically employed to measure torque in industrial robots, humanoid robots, and other similar robots. They operate based on many principles, such as resistive strain gauges, electromagnetic principles, and optoelectronic principles.
This article provides a detailed introduction to robot torque sensors. Hope it proves helpful.
What is a Robot Torque Sensor?
A robot torque sensor is a device that measures the torque applied to a robot. And it converts torque into a usable output signal. It primarily consists of the body unit and the strain/deformation detection system. The core principle of a robot torque sensor is to convert deformation caused by applied force into a signal.
When force is applied, it acts upon the sensor’s body unit. Inducing strain or deformation within it. The detection system senses this strain or deformation. And converts it into a corresponding voltage through circuitry. The measured voltage value characterizes the corresponding torque value. And the torque value is converted into a corresponding output signal.
Advantages:
High Accuracy:
The normal accuracy of ±0.1% FS. Some high-precision models even reach ±0.05% FS. As precision measurement tools, they accurately measure various torques, rotational speeds, and mechanical power.
Exceptional Stability:
Certain customized static torque sensors from Sino-Inst maintain hourly drift within ±0.01% of full scale, with zero drift values confined to an extremely small range.
Wide Measurement Range:
Robotic torque sensors feature a broad measurement range with customizable capacity. Certain models incorporate high-temperature and vibration-resistant designs to accommodate wider measurement spans. Normal measurement ranges span from 0 Nm to 100 kNm.
Easy Installation and Versatile Applications:
Robots’ torque sensor features compact, lightweight, and simplified structural designs for straightforward installation. Torque sensors operate independently of auxiliary instruments. Torque sensors accommodate torque measurement and control for many robotic systems.
Various signal output types:
Output signals can be customized for your special requirements. Optional signal output includes 4-20mA, 0-10V, RS-485, and Hart, etc. It is suitable for long-distance transmission or anti-interference requirements.
Working Principle of Robot Torque Sensors
Robot torque sensors operate on many principles. We should select different types based on adjustable application requirements. Currently, torque sensors developed primarily include strain gauge, magnetoelectric, and photoelectric types. Among these, silicon/metal foil resistive strain gauge torque sensors are widely adopted.
| Detection Methods | Working Principle | Advantage | Disadvantage |
| Electromagnetic | Based on the Hall effect, a corresponding change in magnetic flux is generated under the action of force/torque. |
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| Photoelectric | Based on the photoelectric effect, changes in optical quantities occur in response to applied forces or torques. |
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| Inductive | Under the action of force/torque, a corresponding change in inductance occurs. |
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| Resistive Strain Gauge | Under the action of force or torque, the shape of the strain gauge changes, causing its resistance to increase or decrease with deformation, thereby detecting the magnitude of the force. |
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| Capacitive | Variable capacitance pressure sensors consist of two capacitor plates. Changes in pressure cause the gap between them to narrow or widen, thereby altering the capacitance and detecting variations in force. |
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Robot Torque Sensor Application Scenarios
Robotic torque sensors are primarily used for torque control in robot design.
Balancing while walking poses a significant challenge for humanoid robots. Torque sensors installed on leg joints continuously monitor ground reaction forces and joint stress states. It enables real-time adjustments to gait and center of gravity. They can perform flexible actions like autonomously standing up after a fall with a torque sensor. These sensors allow robots to maintain stability on complex terrain.
During grasping actions, torque sensors continuously monitor the force applied by the gripper. Precise torque data prevents objects from slipping due to insufficient force. It can also avoid damage from excessive force.
For example, during the grasping process, the torque sensor transmits torque to the control system within milliseconds. Accurate torque data enables the robot to flexibly adjust its grasping force. It achieves precision control approaching human tactile sensitivity.
Torque sensors are typically required at each joint of industrial and collaborative robots. This enables robots to execute tasks with greater precision while preventing self-damage. Robotic torque sensors ensure the stability and safety of robotic operations.
Sino-Inst Featured Torque Sensor
Why are torque sensors crucial for robots?
For robots, torque sensors primarily measure the force and torque exerted on the robot’s end effector when it comes into contact with the external environment. Torque sensors provide crucial force-sensing information for the robot’s force and motion control.
Torque sensors play a key role in robotics. Especially for intelligent robots, a robot’s sense of touch and force relies heavily on torque sensors.
Simply, torque sensors are used in robots in the following aspects:
- Enhancing operational accuracy
- Enhancing environmental adaptability
- Optimizing energy consumption.
- Improving perception capabilities
In short, torque sensors are of great significance in promoting the development and application of robotics.
How often should you calibrate a torque sensor?
Each sensor exhibits a unique output due to variations in manufacturing precision. After prolonged use, torque sensors undergo subtle internal material structural changes. The changes are caused by continuous stress release and application, as well as environmental factors like temperature and humidity. Therefore, calibration instruments are required to verify sensor accuracy.
Typically, torque sensors only require calibration once a year. However, in harsh environments, such as those with significant temperature and humidity fluctuations, or when sensors operate continuously at high frequencies. At this time, calibration intervals should be shortened to every 3 to 6 months.
How to calculate torque from RPM?
1. Motors share a common formula: P = MN / 9550
P represents rated power, M denotes rated torque, and N signifies rated speed. Confirming the motor's power and rated speed allows calculation of its rated torque. Note: P is measured in kW, N in RPM (revolutions per minute), and M in Nm (Newton meters).
2. Torque and moment are identical concepts—the product of force and lever arm length, measured in N·m (Newton-meters).
For example, A motor generating 10 Newton-meters of torque at a distance of 1 meter from the output shaft (1-meter lever arm) produces a force of 10 Newtons. At a distance of 10 meters from the output shaft (10-meter lever arm), its output force is only 1 Newton.
Meaning: 1 kilogram = 9.8 newtons. An object with a mass of 1 kilogram experiences a gravitational force of 9.8 newtons on Earth. All in all, robotic torque sensors play a critical role in torque control systems.
Read More about: Torque, Power and Speed of Motor
How much torque do I need for a robot?
The torque required to drive a robot depends on various factors. including the application scenario and the robot’s construction materials.
Typically, robots require approximately 10 to 100 Newton-meters (Nm) of force for operation. To ensure stability during movement, motors used in balancing robots feature high torque. Consequently, the torque of such motors ranges between 10 and 100 Nm.
Sino-Inst is a torque sensor supplier based in China. For technical inquiries, contact us anytime. Our professional engineers provide tailored measurement solutions 24/7. When purchasing perfect robot torque sensors, choose us with confidence.
