What Is a Force Sensor?
A Force Sensor is a sensor that measures the magnitude of a force or moment.
It is used to reproduce the human sense of touch by detecting the amount and direction of physical force. Its main application is in robotics.
Force Sensors are basically 6-axis type Force Sensors, which means they can detect forces in three dimensions (X, Y, and Z) and moments around each of these axes (X, Y, and Z).
Applications of Force Sensors
Force Sensors are used in industrial robots to automate tasks that previously had to be performed manually.
1.Detection of External and Reaction Forces
Force Sensors can simultaneously measure forces and moments. Installed at the work end of a robot, it can work with appropriate force while measuring external and reaction forces.
2. Automation of Precision Work
Force Sensors can measure accurate forces and moments so that robots can work with appropriate forces. This enables automation of precision work by robots.
Specific tasks include insertion of electronic components and connectors with soft terminals, mating with little play, precision screw tightening, deburring, polishing with subtle force, picking work, and independent control of a biped robot.
3. Tactile Diagnosis and Remote Medical Treatment
A terminal equipped with a Force Sensor can be positioned beside a patient, allowing a doctor to access and interpret the forces and moments detected by the Force Sensor, which enables remote tactile diagnosis.
Principle of Force Sensor
Force Sensors detect the amount of deformation caused by a force and convert it into a force or moment.
Strain gage, piezoelectric, optical, and capacitive force sensors are representative among the detection methods of Force Sensors.
1. Strain Gage Type Force Sensor
The strain gage type is a method of converting force or torque by utilizing the property of metal resistive materials whose electrical resistance changes according to the tensile or compressive force applied to the sensor part. This method is widely used for force sensors because it is compact, highly accurate, and responsive.
2. Piezoelectric Force Sensor
Piezoelectric Force Sensors use piezoelectric materials such as quartz crystal or PZT (lead zirconate titanate) for the sensor part to measure force. They are compact, highly responsive, and relatively inexpensive. However, the accuracy is not as high as strain gage type or capacitance type.
3. Capacitive Force Sensor
The structure of the capacitive type sensor involves electrodes made of metallic materials arranged facing each other in a capacitor-like configuration. This method detects changes in capacitance due to changes in distance caused by strain between conductors due to force.
The capacitance type is characterized by its relatively simple configuration and low cost. If the electrodes are made of film, they can be made smaller and thinner. Accuracy and response are also excellent.
4. Optical Force Sensor
In the optical method, a pattern is marked on the object to be measured at regular intervals. The change in the pattern that occurs when a force is applied is detected by an optical sensor such as a camera or laser, and the magnitude of the force is calculated and obtained.
The greatest advantage of the optical method is that it enables non-contact measurement. On the other hand, accuracy, responsiveness, miniaturization, and cost are inferior to other methods. It is limited to special applications that require non-contact measurement.
5. HDR Force Sensor
There are what are called HDR (High Dynamic Range) Force Sensors, which are characterized by a wide dynamic range, e.g., from 10 g to 20 kg.
By combining AI and robot technology with HDR Force Sensors, fine assembly operations can be performed while adjusting for minute forces. Robots are increasingly automating and upgrading assembly work at production sites.
6. Capacitive Force Sensor
The capacitive Force Sensor is characterized by its ability to measure 6-axis components by detecting changes in the distance between two parallel plates. A simple structure can be realized and the price can be kept low.
Force Sensors with an anti-overload stopper mechanism inside the sensor are also available. Recently, these sensors are widely used in the industrial robot field. Demand is expected to grow more and more due to the increasing automation in the manufacturing industry.
Other Information on Force Sensors
Application of Force Sensors
Cooperative work between humans and robots can be realized by having humans operate robots that use Force Sensors. Fine work that requires minute force adjustment can also be performed.
In particular, in the manufacturing field, the use of Force Sensors has realized automation of tasks that can only be performed by skilled craftsmen, thereby improving productivity. In the medical field, Force Sensors are expected to be used in remote medical examinations where the condition of the affected area can be determined by tactile diagnosis.