I. Considering the range of force and torque
Evaluate the range of forces and moments in the application scenario.
First, a detailed analysis of the specific application scenarios of industrial robots is necessary. For example, in the car body welding scenario in automobile manufacturing, the robot mainly applies a small contact force to ensure good adhesion of the welded car body surface, and this force is generally between a few Newtons and tens of Newtons; while in heavy machinery assembly scenarios, such as the assembly of large engines, the robot may need to withstand and measure forces of hundreds or even thousands of Newtons and large torques.
In electronic product assembly scenarios, such as chip packaging, the force exerted by the robot is usually very small. It may only require a sensor with a range of a few millinewtons to a few newtons to precisely control the force and avoid damage to delicate electronic components.
Leave a certain margin
When determining the force and torque range, it is recommended to choose a range slightly larger than the maximum possible value in the actual application scenario. This is to prevent the sensor from being damaged due to overload in unexpected situations, such as robot collisions or encountering unexpected loads. Generally, allowing a margin of 10% - 30% is appropriate. For example, if the expected force is 100N, choosing a sensor with a range of 120 - 130N is safer.
II. Accuracy Requirements
The degree of accuracy required for analytical applications
Different industrial robot applications have vastly different precision requirements. In high-precision medical surgical robot applications, extremely high precision is required. For example, in neurosurgery, the precision of a six-dimensional force sensor may need to reach the millinewton level or even higher to ensure that surgical instruments do not damage nerve tissue during operation.
In scenarios where precision requirements are relatively low, such as ordinary logistics handling robots, the precision requirements can be appropriately relaxed. These scenarios primarily focus on whether the robot can stably transport goods; the requirements for precise measurement of force and torque are not particularly high, and sensor accuracy at the level of a few Newtons may be sufficient.
Considering the linearity and repeatability of the sensor
Linearity refers to the degree of linearity between the sensor's output signal and the input force and torque. Good linearity ensures the accuracy of measurement results, especially in applications requiring precise force control. For example, in pressure testing equipment for electronic components, the linearity deviation of the sensor is required to be within a very small range to guarantee the reliability of the test results.
Repeatability refers to a sensor's ability to obtain the same result multiple times under the same input conditions. In automated production lines with industrial robots, sensors with good repeatability ensure consistency in each operation. For example, in the tightening of automotive parts, sensors need good repeatability to ensure that the tightening torque of each screw meets the standard.
III. Response Frequency
Determine the required speed and frequency of actions in the application scenario.
Observe the movement speed and motion frequency of industrial robots in application scenarios. In high-speed packaging robot applications, the robot arm may need to quickly grasp and place items, which requires a six-dimensional force sensor with a high response frequency. If the sensor response is too slow, it may miss the peak of force changes, resulting in inaccurate control of the robot's movements.
Conversely, in slow-moving processing scenarios, such as grinding large ship components, the robot's movement speed is slower, and the requirements for sensor response frequency are relatively lower. In this case, a sensor with a slightly lower response frequency but superior performance in other aspects can be selected.
Matching the robot's control cycle
The sensor's response frequency should match the robot's control cycle. Generally, the sensor's response frequency should be at least several times the robot's control cycle frequency to ensure that force and torque information can be received and processed by the robot's control system in a timely manner. For example, if the robot's control cycle is 10ms, the sensor's response frequency should ideally be above 100Hz.
IV. Installation Method and Dimensions
Considering the structural and space constraints of the robot's end effector
The structures of end effectors (such as grippers, suction cups, and tools) of industrial robots vary, and therefore require different installation methods for six-dimensional force sensors. For some end effectors with complex structures, it may be necessary to select small sensors with flexible installation methods. For example, in robot grippers used for sorting small electronic parts, due to limited gripper space, it is necessary to select sensors that are small in size and can be easily integrated into the gripper.
For heavy-duty tools used by large industrial robots (such as large welding equipment or heavy assembly tools), the robustness and stability of sensor installation must be considered. The sensor mounting method may need to be able to withstand significant forces and torques, and must ensure that it does not loosen during extended robot operation.
Ensure that the installed sensors do not interfere with the normal operation of the robot.
The installation of a six-dimensional force sensor must not affect the function and normal operation of the robot's end effector. For example, when the robot's suction cup is used to move objects on smooth surfaces, the sensor installation must not change the suction performance of the suction cup, nor should it obstruct the contact area between the suction cup and the object; otherwise, the handling effect will be affected.
V. Adaptability to the working environment
Environmental conditions for evaluating application scenarios
Industrial robots operate in a variety of environments, including those affected by factors such as temperature, humidity, dust, oil, and electromagnetic interference. In high-temperature metallurgical industrial settings, such as continuous casting robots in steel plants, six-dimensional force sensors need to withstand high-temperature environments. Generally, the sensors are required to operate normally at temperatures of several hundred degrees Celsius while ensuring that measurement accuracy is not significantly affected.
In humid or corrosive liquid environments, such as chemical production workshops, sensors need to have good waterproof and corrosion-resistant properties. The housing material may need to be made of special anti-corrosion materials, and the sealing performance must be good to prevent liquid from entering the sensor and damaging the electronic components.
Considering electromagnetic compatibility
If industrial robots operate in environments with strong electromagnetic interference, such as near large motor equipment or high-frequency welding equipment, the six-dimensional force sensor needs to have good electromagnetic compatibility. This means that the sensor can function normally in such an electromagnetic environment and will not generate erroneous measurement signals due to electromagnetic interference, thus affecting the robot's control and operation.
