Since 2007, collaborative robots have begun to enter industry, exploring their potential for widespread use in various applications. After 2014, the collaborative robot industry experienced a surge in growth, with collaborative robots becoming a hot topic in robotics, attracting significant capital investment and prompting strategic planning from businesses. However, collaborative robots involve various technological approaches, some with proven viable models, while others are still in the trial-and-error phase. Driven by capital, wave after wave of startups have entered the market, making the road ahead bumpy and the future uncertain.
In September 2017, the International Federation of Robotics (IFR) released its market forecast for 2017-2020. In its main report, it emphasized future trends:
•Robots which are easier to install, program and operate will unlock entry barriers to the large, untapped market of small and medium enterprises (SMEs).
•Trendtowards having production closer to the end consumer driving the importance ofstandardisation & consistency across global brands.
•Collaborativerobots are shifting the traditional limits of “what can be automated?”
•Collaborativerobots increase manufacturing flexibility as 'lowvolume high mix' becomes the new normal
•Collaboration is also about productivity with increased human/robot interaction
To summarize the trends observed by the International Federation, we can say that simple, easy-to-use, flexible, safe, and collaborative robots will better meet the diverse production needs of SMEs and global enterprises, becoming the primary trend in industrial robot development .
Why have collaborative robots emerged as a trend in robotics development? This topic requires discussing the maturity of robots' applications and technological advancements since their inception. One classic robot in particular has played a crucial role in driving the development of robotics .
Engelberger was the inventor of the world's first true robot . In 1959, Engelberger and Devol invented the world's first industrial robot, Unimate. It was large and cumbersome, using a hydraulic actuator, and could only perform the simplest handling tasks.
Engelberger was the inventor of the industrial robot, and his company was a pioneer in industrial robotics . The products of this company, Unimation, are still active in the robotics world, although the name Unimate is not commonly seen. Instead, a company called Staubil integrated and developed Unimation's products—but that's another story.
Unimation holds a very important position in the robotics world. Let's first look at the company's history . Founder Engelberger was born in New York in 1925 and earned a bachelor's degree in physics and a master's degree in electrical engineering from Columbia University. In 1950, Engelberger read Isaac Asimov's short story collection *I, Robot*, and was captivated, sparking the idea of building robots. At a party in 1956, he met inventor George C. Devol. Devol mentioned that he had just applied for a patent called "Programmed Article Transfer." Engelberger exclaimed, "Isn't that Asimov's robot?!" The two hit it off immediately and decided to collaborate to found a company that produced robots—Unimation.
In 1958, Unimation created a robotic arm that resembled a human arm in shape—what we now commonly call a robot . This robot possessed dexterity similar to a human hand, but it was also extremely expensive, making it affordable only to large corporations at the time. Therefore, Engelberg targeted large companies as potential users for his robot.
In 1961, after a long period of effort and explanation, General Motors installed and used the first Unimation robot at a plant in New Jersey. This was the first recorded instance of a robot used in industry . Compared to humans, this robot had significant advantages in use. For example, it could work tirelessly and efficiently in repetitive tasks such as welding and material handling; it also had advantages over humans in toxic or other hazardous environments.
General Motors began ordering more robots, which were installed in factories around the world, taking on tasks ranging from welding and painting to bonding and assembly. This use made GM the first automaker to automate production, consolidating and expanding its industry-leading position . Meanwhile, other automakers such as Ford and Chrysler followed suit, incorporating robots into their own car production lines.
In this way, robots began to be used first in the automotive industry!
Unimation later licensed its technology to Kawasaki Heavy Industries and GKN, who manufactured Unimate robots in Japan and the UK respectively . Subsequently, the Japanese automotive industry began to introduce robots, deploying them on production lines to replace manual labor. The Japanese, with their meticulous work ethic and pursuit of excellence, fully utilized the value of robots . Later, Japan gave rise to many world-class robotics companies, from Kawasaki, which initially introduced robot technology, to later joint ventures such as FANUC and Yaskawa, establishing Japanese robotics companies as a significant force in the industry .
Robots used in large-scale automobile production are generally referred to as traditional robots . Since their introduction into industrial production, robots have consistently held a crucial position in the automotive industry. Statistics show that before 2010, robots used in the global automotive industry already accounted for 37% of the total, with industrial robots used for automotive parts accounting for approximately 24%, totaling over 50% of the industry's usage. In some countries, such as the United States, Europe, and Japan, the proportion may be even higher.
Thus, the application of robots in the automotive industry has a broad foundation. The product forms of various robot companies are more diverse, with serial robot technology being the most competitive and having the widest range of applications in various situations .
In 2003, Esben Østergaard was conducting research at the University of Southern Denmark, searching for user-friendly, flexible solutions for the food industry that could adapt to product switching. He and his partners, Kasper Støy and Kristian Kassow, searched the market for all existing robots but couldn't find one that was both flexible and easy to use, requiring no special protection. At the time, the main products on the robot market were large, expensive, and cumbersome. As mentioned in our article, "Unveiling Why Rethink Collapsed! 'Collaborative Robots - Who Can Break Through the Fierce Market?'", Rodney Brooks, while searching for factories to manufacture for iRobot, discovered that existing factories couldn't meet the production requirements. This sparked the initial idea of creating a user-friendly and inexpensive robot. There is little publicly available information about this history online. iRobot's business was not initially focused; military projects were its primary business for the first 10 years of the company's existence. iRobot's involvement in civilian service robots began after 2002, which is a major reason for the company's growth and eventual IPO. Before Rodney Brooks founded Rethink in 2008, we speculate that between 2005 and 2007, he discovered that the factory's production did not match his needs, which led to the idea of creating an easy-to-use, flexible, and inexpensive robot.
In 2005, Esben Østergaard, Kasper Støy, and Kristian Kassow founded Universal Robots, based on the idea of "developing a lightweight robot that is easy to install and use," and dedicated to developing robot technology that small and medium-sized enterprises could afford. This idea was similar to the initial intention of Rodney Brooks when he founded Rethink Robotics. That same year, the Danish National Investment Fund approved the proposal of the Syddansk Innovation Fund and, together with the Syddansk Innovation Fund, participated in the investment and management of Universal Robots. Subsequently, Universal Robots' products gained widespread attention, and to date, UR Robots holds the largest market share among collaborative robot manufacturers, leading the development of the collaborative robot industry.
The reasons for the rise of collaborative robots can be summarized as follows:
After 2000, we saw an urgent need to transform the way robots are used. In the automotive industry, where robot use is concentrated, large-scale factories are rarely being built in developed countries anymore. For example, BMW recently announced a €1 billion (US$1.17 billion) investment in a new assembly plant in Hungary, its first factory in Europe in nearly two decades. On the other hand, large-scale industrial production gradually shifted to countries with lower labor costs, such as those in Asia, after 2000. Large-scale manufacturers, leveraging the demographic dividends of countries like China, Vietnam, and Thailand, gradually moved their factories out of Europe, and even low-cost industrial consumer goods manufacturers gradually closed down because importing products from developing countries was cheaper. We say that profit-seeking is the root of all evil in capitalism, and this is an undeniable fact for business competition.
Taking Europe as an example, following the planned relocation of industrial production, there are a large number of small and medium-sized enterprises (SMEs) that cannot be transferred . SMEs are an important component of economies worldwide. While the definition of SMEs varies across economies and dynamically changes with economic development, their crucial role in the economy is undeniable. In Europe, over 95% of business activities are conducted by SMEs, and 60-70% of employees work for them. In the United States, SMEs account for 99.9% of all businesses, employing approximately 120 million workers (excluding agricultural workers), 50% of whom work in SMEs. For example, the food industry is widespread in Europe, supplying cheese, bread, vegetables, and other daily necessities to Europeans. Due to supply volume and shelf-life considerations, production cannot be transferred to other countries, thus necessitating its preservation locally.
The launch of any new product or technology is an iterative update based on the current product, resulting in a more complete product, and the robotics industry is no exception.
In the 1980s, the emergence of a classic robot played a very important role in promoting the development of robotics—the PUMA-560.
The PUMA-560 robotic arm, also a product of Unimation, is a classic industrial robot in robotics history. It has 6 degrees of freedom, a 2kg payload, and uses DC servos. The PUMA-560 employs a human-like mechanical structure, consisting of a series of rigid links connected by a series of flexible joints in a series of alternating links. The joints are connected by links, similar to the connection in a human arm, with central movable joints connecting the upper and lower arms, similar to a human's upper arm. In comparison to a human, the robotic arm's body is equivalent to the shoulder, elbow, and wrist joints .
The creation of the Puma series of robots has had a significant impact on both industrial and scientific research fields. Beginners in robotics often use this robot as a foundation, further verifying and improving forward and inverse kinematics problems through traditional computational methods such as analytical and iterative approaches . A series of classic robotics textbooks use the Puma 560 as a teaching tool to explain the theory of industrial robots. For example, John F. Fuchsson's *Robotics*, a classic textbook on robotics, remains relatively comprehensive even today, and is still widely used as a textbook for graduate students in several renowned robotics research institutes in China .
The development of robot dynamics and kinematics, along with the emergence of new transmission and drive mechanisms and intelligent and soft matter materials, suggests that flexibility, softness, adaptability, miniaturization, and intelligent control will make the emergence of new functional robots possible.
Robots, in their various forms and movements, remain biomimetic, similar to living organisms. This structure dictates that from Puma to the emergence of new robots, there shouldn't be significant deviations . For example, while the internal structure of new energy vehicles has changed considerably, their form remains the same as traditional gasoline-powered cars; they haven't become six-wheeled or strangely shaped. The internal combustion engine has been replaced by new AC/DC motors, and the fuel has been replaced by rechargeable nickel-metal hydride batteries. The result is that new energy vehicles offer more sophisticated intelligent connectivity systems, such as human-vehicle interaction, meeting diverse human needs and further stimulating consumer enthusiasm.
Sixty years after their deployment, a growing bottleneck for traditional robots is their lack of interactivity. Interactivity manifests in three aspects:
(1) Easy to use
Ease of use is most directly demonstrated through drag-and-drop teaching . Using the robot's dynamic model, the controller can calculate in real-time the torque required to drag the robot, and then supply that torque to the motors, enabling the robot to effectively assist the operator in dragging. The torque calculation is shown in the following formula:
The formula contains the torque required by the motor, calculated using inverse dynamics. The calculation formula includes inertial force, Coriolis force, centrifugal force, gravity, and friction . Depending on the chosen friction model, the friction force can be decomposed into viscous friction, Coulomb friction, and compensation.
Calculating friction involves a relatively complex mathematical model. Current technological approaches include sensorless compensation, using external force sensors for feedback optimization, and employing elastic device extension/retraction models. Each robotics company has unique advantages in this step, enabling zero-gravity dragging and teaching functions .
(2) Flexibility
To enhance human interaction, robots need to be used as tools, requiring greater flexibility in their application . The robot itself must be lightweight, allowing workers to move and easily install it as needed, enabling it to be deployed quickly.
Hollow frameless motors are directly integrated into the joint axes, forming a modular structure. The motors can be embedded in the robot's base and directly drive the load, enabling high-precision horizontal movement and force control. During operation, they can recognize the size and flexibility of the object and adjust the applied force accordingly. The modular structure allows for faster interchangeability between joints of the same type; if a joint malfunctions in the robot, it can be replaced within 10-30 minutes.
At the same time, the weight of the robot body has been further reduced, achieving a special ratio of net weight to load-bearing capacity, all of which are the result of advanced lightweight structures.
(3) Safety
When robots interact with humans, human safety must be guaranteed, and collision detection is an essential function that collaborative robots must achieve.
Traditional robots also have collision detection capabilities, but the purpose of collision detection in traditional robots is generally to reduce the impact of collision forces on the robot body and avoid damage to the robot body or peripheral devices.
Collision detection in collaborative robots aims to address the challenge of human-robot coexistence . It can be implemented using methods such as force-sensing sensors, joint torque sensors, and current-based force feedback models. The implementation must accurately reflect the collision force settings to allow for flexible force adjustments in various environments.
Assuming ease of use, flexibility, and safety are met, reliability is an absolute must . Ultimately, ease of use, flexibility, and safety address the challenges operators face during setup, further reducing this time to perhaps only 10% or less of the robot's lifespan. For the rest of the time, robots remain on the production line, performing monotonous, repetitive tasks. During this period, industrial efficiency will revert to the traditional robot usage model, with factories focusing on cycle time and output. Collaborative robots must achieve similar reliability requirements as traditional robots.
Collaborative robots, designed to adapt to changing production relationships and methods, are destined to solve the production challenges that have emerged since the beginning of the 21st century . They can flexibly cooperate with humans, quickly deploying in production for applications such as material handling, screw tightening, and polishing. Applications that previously took days or even weeks to complete can now be finished in one or two days, or even within hours. While collaborative robots do have some limitations, such as lower load capacity and slower speed, they can meet the needs of most production applications. The increasing number of successful case studies has given customers greater confidence in their use, leading to the booming development of the collaborative robot industry.
