With the advent of the 5G era, the industrial manufacturing sector is ushering in a brand new transformation, a round of innovation stemming from the breakthrough development of a new generation of information technology, as well as changes in market demand and a strong policy push. As a result, the manufacturing industry has to be transformed and upgraded to take manufacturing to a new level by integrating new technologies.
Robot grinding market
From the perspective of national policy, the core sensor is a very important cornerstone of the Industry 4.0 era, in the "Made in China 2025", the "Thirteenth Five-Year Plan" national science and technology innovation plan, "a new generation of artificial intelligence development plan" and many other plans inside, all the sensor research and development as one of the planning priorities. Some relevant institutions predict that by 2025 China's industrial Internet market size will reach 10.8 trillion yuan, of which, the sensor as the data collection portal, the industrial Internet "heart", will usher in a huge space for development.
At present, sensor systems are also developing in the direction of miniaturization, intelligence, multi-functionality and networking. Data compiled by the China Academy of ICT Foresight Industry Research Institute shows that the sensor market size reached 147.2 billion yuan in 2018, an increase of more than 10% year-on-year, and it is expected that in 2023, the sensor market size in China will reach 270.3 billion yuan. In terms of grinding process, it is roughly divided into four types, i.e. grinding process, rough grinding, fine grinding, deburring (removing the thorns or flying edges formed around the machined parts of the workpiece).
Pain points in the traditional sanding industry
At present, the following pain points are common in the traditional industrial grinding industry: firstly, the danger factor is high, as the dust generated by traditional grinding is not discharged in time, which can easily lead to explosions and endanger personal safety; secondly, the consistency of the workpiece is poor, as the quality of grinding is closely related to the workers' methods, and the quality of the workpiece varies; thirdly, the production efficiency is low, as traditional manual grinding is inefficient and there is also the problem of high scrap rate; fourthly, the cost of labour is high, and the recruitment and retention of workers is high. High labour cost, difficult to recruit and retain workers.
Advantages of robotic grinding
Compared to traditional manual grinding, robotic grinding has the following advantages: an enclosed robot workstation isolates high noise and dust from the outside, reducing environmental pollution; the operator does not come into direct contact with dangerous processing equipment, avoiding workplace accidents; the robot can ensure the accuracy of product processing consistency, which not only ensures reliable quality but also reduces the scrap rate;
The robot replaces skilled workers, which not only reduces manpower costs, but also does not affect delivery times due to the loss of operators; the robot can work continuously 24 hours a day, which significantly increases production efficiency; the user can develop secondary programming for different parts, shortening the product change cycle and reducing the corresponding investment in equipment.
What is a six-dimensional force sensor?
Our topic today is "Six-dimensional force sensors in industrial grinding and assembly", so what is a six-dimensional force sensor?
Let's start by getting to know force sensors, which are a class of tactile sensors that have a wide range of applications in robotics and mechatronic equipment. Force and torque sensors are used for the purpose of detecting forces within a device or forces interacting with the external environment. Forces are not directly measurable physical quantities; they are measured indirectly through other physical quantities.
Force sensors can be used as transformers, such as strain gages, which provide a signal proportional to the deformation, i.e. the force acting on the contact point. Force sensors can detect external forces and torques applied to relevant parts of the robot (e.g. wrist, fingers) and can control wrist movement, servo control and accurate job completion.
Six-dimensional force sensors are a newly developed type of force sensor that can simultaneously convert multi-dimensional force/moment signals into electrical signals and can be used to monitor forces and moments of changing direction and magnitude and to measure acceleration or inertia forces as well as to detect the magnitude and point of action of contact forces.
Generalised six-dimensional force sensors are capable of checking three-dimensional orthogonal forces (fx, fy, fz) and three-dimensional orthogonal moments (mx, my, mz) in any force system in space, and are mainly used in force and force-position control applications due to their rich force measurement information and high measurement accuracy.
Current status of research on six-dimensional force sensors
International research on multidimensional force sensors began in the early 1970s, with major research units such as DRAPER Laboratories, SRI (Stanford Research Institute), JPL Laboratories, IBM and Hitachi in Japan, and the University of Tokyo.
Domestic research on six-dimensional force sensors began in the early 1980s, with the first six-dimensional wrist force sensor developed by the Hefei Institute of Intelligent Machinery, Chinese Academy of Sciences in 1987. The development of multidimensional force/torque information acquisition research in China has been flourishing. At present, more research institutions in the six-dimensional force sensor are Yanshan University, HUST, Dalian Polytechnic University, etc.
In recent years, research hotspots have focused more on the application areas of multidimensional force/torque sensors, such as how modern industrial robots can make full use of multidimensional force/torque sensors and other sensing systems to complete more and more complex robot operations in various environments, making the work more accurate, more productive and less costly; such as the use of multidimensional force/torque sensors to industrial robot automatic assembly lines, combined with more real-time and more effective algorithms, enabling intelligent industrial robots to better perform precision and flexible mechanical assembly, contour tracking and other operations.
In the study of six-dimensional force sensors, the structural design of the force sensitive element is a key core issue for force sensors, as the structure of the force sensitive element determines the performance of the force sensor. In this regard, many international and domestic scholars have carried out a lot of research work and proposed a variety of six-dimensional force sensor structures
Six-dimensional force sensors in industrial grinding
The main areas of application for six-dimensional force sensors at industrial level are assembly and grinding, and grinding is an area where robots are widely used. This, coupled with the need for flexibility in the 3C industry, requires more intelligent grinding robots to better meet market demand.
The six-dimensional force sensor is fixedly connected to the end joint of the robot arm by means of a sensor mount. Under static conditions, the force and torque data measured by the six-dimensional force sensor on the mechanical wrist consists of three components: the sensor's own system error, the gravitational effect of the load, and the external contact force applied to the load. In industrial robot applications such as machining and assembly, the contact force between the robot's end tool or workpiece and the external environment needs to be accurately sensed, and the control system modifies the robot's motion accordingly in order to ensure a supple operation.
Market challenges for sensors
Although the six-dimensional force sensor can reach six dimensions of freedom in the robot, greatly enhancing the robot's intelligence, the current use of the industrial market is not very optimistic, especially in the domestic market using six-dimensional force sensor grinding robot products are not many.
Currently there are more ways to use floating spindles with single-dimensional force control. There are two main reasons for this: 1. In industries with low requirements for precision grinding, the current force sensors can meet the needs of the grinding process, and companies are not willing to spend more to buy grinding equipment equipped with six-dimensional force sensors; 2. The current price of six-dimensional force sensors is relatively expensive, and the cost of upgrading is high.
Market opportunities for sensors
With the development of industrial processing, manufacturing more and more refined, precision assembly industry such as 3C industry requirements for the production of robots will also improve, with higher performance sensors such as six-dimensional force sensors will also usher in new development opportunities. At present, more than 90% of industrial automation operations cannot be completed by traditional robots, including precision grinding, precision assembly, mechanical management, material preparation, loading and unloading, and packaging, which have not yet been fully automated. The global robotics industry and related services market was $71 billion in 2015 and is expected to reach $32 billion in 2019. As an important component of human-machine collaborative robots, six-dimensional force sensors play a vital role in human-machine collaborative applications.
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