Potential market size of speed reducers in China
According to research by industry experts and associations, precision reducers used in the robotics industry globally can be categorized into RV reducers, harmonic reducers, and SPINEA reducers, with market sales accounting for approximately 40%, 40%, and 20% respectively. Among these, RV reducers and harmonic reducers are the most mainstream precision reducers for industrial robots.
RV reducers are characterized by large transmission ratio, high transmission efficiency, high motion accuracy, low backlash, low vibration, high rigidity, and high reliability. In articulated robots, RV reducers are typically placed in heavy-load positions such as the base, upper arm, and shoulder.
Harmonic reducers: They have a large transmission ratio, small overall size, few parts, and high transmission efficiency. In articulated robots, harmonic reducers are typically placed in the forearm, wrist, or hand.
It is estimated that China will need 190,000 robots annually by 2020, achieving a 50% domestic market share (95,000 units) by 2020, and exceeding 70% by 2025. This represents a potential market of over $74 billion for robots and related services for Chinese manufacturers over the next five years. With the rapid development of my country's industrial robot application market, the demand for industrial robot reducers is also growing. Typically, one industrial robot requires 4-6 reducers. Based on the future development of industrial robots, the China Investment Consulting Industry Research Center predicts that the market size of industrial robot reducers in my country will exceed 4 billion yuan by 2020, with a compound annual growth rate of approximately 30% over the next five years.
According to industry insiders, the four major international giants purchase a precision reducer for 30,000 to 50,000 yuan, sell it to domestic customers with good relationships for about 70,000 yuan, and to ordinary customers with average relationships for about 120,000 yuan. The cost for domestic enterprises to purchase precision reducers is more than double that of international giants, which shows how big the profit difference is.
Current Market Status of Gear Reducers in China
For a long time, the technology of precision reducers for robots has been controlled by countries such as the United States, Germany, Japan, and the Czech Republic. Among them, 75% of the world's precision reducer market is occupied by Japanese companies Harmonic Drive and Nabtesco. Nabtesco produces RV reducers, accounting for about 60% of the market share, while Harmonic Drive produces harmonic reducers, accounting for about 15% of the market share.
In terms of cost, the current global robotics industry costs approximately 35% for reducers, 20% for servo motors, and 15% for control systems. The machining of the robot body itself likely accounts for only about 15%, with the remainder primarily related to applications. It's clear that reducers are a key factor restricting the development of the robotics industry. Currently, China lacks overall breakthroughs in core robotics technologies, leading to the slow development of the robotics industry in my country's high-end equipment manufacturing sector, which relies heavily on imported RV reducers.
A high import ratio of key components leads to high costs for domestic robot manufacturing. This is especially true for speed reducers, where domestic companies often pay several times more than foreign companies. This makes it difficult for domestically produced robots to achieve a price advantage; only an annual production volume of 500-1000 units can achieve economies of scale. Therefore, if China wants to industrialize its robot industry, break free from the constraints of foreign robot companies, and gain autonomy in the field, it must accelerate the localization of speed reducers.
Currently, the development of speed reducers faces bottlenecks in capacity expansion, involving issues related to toll collection, management, and technology. Japanese speed reducers are experiencing delayed delivery cycles, with the longest exceeding six months. Nabtesco's delivery cycle has extended from 2-3 months to 4-6 months. Domestic speed reducer production capacity cannot achieve a significant increase in a short period, failing to meet the ever-expanding market demand. Therefore, capacity expansion is not only a problem facing domestic speed reducers but also one of the challenges faced by Japanese speed reducers.
The technological gap in RV reducers
The technology required for RV reducers is very advanced. The core challenge lies in the close coordination of various processes.
Tooth surface heat treatment is an input condition; stress residue under rough machining precision must be considered, and the surface stiffness and strength must be consistent during heat treatment.
Machining precision, the hard outer surface and soft inner surface of the heat-treated surface, and the varying removal amounts during machining all contribute to the variance in the performance of the exposed portions.
The symmetry of the parts must be maintained; different parts must appear consistent at different angles.
Group technology: How to coordinate among groups;
Assembly precision: Such a high degree of precision in assembly;
The overall distribution of the above tolerances results in wear and lifespan;
In terms of power
Simulation challenge: Only after the multibody dynamics simulation is completed and the dynamics are modeled can the characteristics of each order of vibration be known;
The nonlinear characteristics cause significant differences, and if a resonance point exists near the operating point, it will be affected;
Coupling with system integration can cause component damage if the operating point (rated speed) of the integrated robot is used as the excitation frequency. Since the system's operating range is often continuously variable, one axis of a 6-axis robot may always be near 20% of its rated speed unless properly designed and implemented.
The product parameters fluctuate greatly. In such a precisely fitted system, even a slight deviation in clearance/interference fit can result in a difference of several times in contact stiffness/meshing stiffness. The huge change in the stiffness matrix causes fluctuations in the natural frequency.
Lifetime optimization and iteration
The lifespan of a stable car and a car that vibrates can differ by many times; it's easy to see where the lifespan goes.
Some material issues cannot be discovered without undergoing full lifecycle testing in real-world environments. Therefore, it is essential to have a phase where problems arise, followed by iterative design iterations.
The current problem facing robots seems to be that 60% of the price can't produce anything, and 90% of the price can produce something with 30% of the lifespan. In fact, lifespan itself is a marker of the level of the mechanical industry.
There are management problems in the RV reducer industry.
Domestic reducers have consistently referenced imported reducers of similar models, without ever having a reducer specifically customized for a particular domestic robot. An industrial robot requires more than just a reducer; its integration with servo and motion control systems is crucial for achieving high precision and stability. Each company's technology differs, and no two foreign robot manufacturers claim their reducers are interchangeable. Domestic reducers focus on achieving performance closer to foreign brands, not on finding the best fit for domestic robots. If this approach is wrong, subsequent use requires constant coordination, refinement, and further refinement between robot manufacturers and domestic reducer manufacturers. For R&D engineers, the development cycle simply cannot afford such time. Therefore, there should be an industry standard for managing reducer R&D and production, developing reducers specifically for Chinese robots.
Currently, most RV reducers used in industrial robots are from Japanese brands, followed by South Korea and the Czech Republic. Nearly 75% of the precision reducers used worldwide by international robot manufacturers such as ABB, Fanuc, and Kuka are manufactured by Japanese companies.
Reducers from well-known domestic and international companies
Direct drive motors, modular direct drive motors and robot joint modules
If chips are the most important core components in the smart industry, then motors are arguably the most important components supporting the entire automation and large-scale industrial production as well as modern society. 90% of the energy is generated by motors, and 70% is consumed and controlled by motors. Motors can be said to be the product that occupies an absolute position in the energy cycle of the entire human society.
ordinary servo motor
Servo motors are considered a high-end type of electric motor, especially permanent magnet synchronous servo motors. Due to their advantages such as fast start-up, low inertia, smooth operation, wide speed range, high power density, and high efficiency, their adoption rate in high-end equipment is increasing year by year. Most servo applications use a reducer + motor transmission method. While the initial cost of traditional systems is attractive, and their performance has been widely adopted in various applications, the reducer + motor transmission method, due to transmission backlash, can lead to cumulative errors in high-precision applications. Therefore, the requirements for servo motors and servo drivers are particularly high, and the lifespan of reducers is also decreasing, increasing the total lifespan cost. Users have to manage more component inventory, and the system failures caused by these additional components increase unplanned downtime, leading to a decrease in machine output.
Direct drive rotary motor
A direct-drive rotary motor is essentially a high-torque disc-type permanent magnet motor that is directly connected to the load. This design eliminates all mechanical transmission components such as gearboxes, belts, pulleys, and couplings. Direct-drive rotary systems offer numerous benefits to designers and users. Because mechanical transmissions require regular maintenance and frequently cause unplanned downtime, direct-drive rotary motor technology fundamentally improves machine reliability, reduces maintenance time, and simplifies control.
Frameless direct drive rotary motor
Frameless direct-drive rotary motors are the "grandfather" of direct-drive motor technology, and they undoubtedly offer the most compact mechanical servo solutions available today. Frameless direct-drive rotary motors use separate rotors and stators, eliminating the use of bearings. These components become an integral part of the machine, also including the necessary feedback mechanisms. They are ideal for applications where space is limited or where overall weight is critical.
These motors are essentially custom-made, making them more expensive and requiring weeks or even months of design and integration time. Furthermore, replacing the motor or feedback device in case of system failure is extremely complex. Therefore, frameless direct-drive rotary motor technology is not suitable for every application. Its most widespread applications are in airborne and ground vehicles, such as aiming control for night vision devices, radar systems, and weapon systems, as well as high-end industrial applications with strict requirements for size, weight, or performance, such as robots or precision grinding machines.
Integrated direct drive rotary motor
An integrated direct-drive rotary motor integrates the rotor, stator, and pre-aligned feedback mechanism into a single housing with precision bearings, offering a complete solution. Integrated direct-drive rotary motors are ideal for applications where the load can ride on the motor bearings. For motors already using bearings, connecting the motor to the load or aligning three or more bearings is a laborious and time-consuming process. Therefore, integrated direct-drive rotary motors are generally used in indexing and rate turntable applications.
In summary, direct drive motors have the following advantages.
Direct drive. The motor and the driven workpiece are directly and rigidly connected, eliminating the need for intermediate components such as lead screws, gears, and reducers. This minimizes the problems of backlash, inertia, friction, and insufficient rigidity inherent in lead screw transmission systems.
High speed. The normal peak speed of a linear motor can reach 5-10 m/s, while the speed of a traditional ball screw is generally limited to 1 m/s, and the wear is also higher.
High acceleration. Due to the absence of contact friction between the mover and stator, linear motors can achieve high acceleration. Larger linear motors are capable of achieving accelerations of 3-5g, while smaller linear motors can achieve accelerations of 30-50g or more (wire bonding machines).
High precision. The use of direct drive technology significantly reduces errors introduced by the intermediate mechanical transmission system. High-precision grating detection is employed for position positioning, further enhancing system accuracy and achieving a repeatability accuracy within 1µm, meeting the requirements of ultra-precision applications.
Wide range of motion speeds. The linear motor can operate at speeds ranging from a minimum of 1µm/s to a maximum of 10m/s, meeting the needs of various applications.
It features low noise, simple structure, low maintenance cost, and can operate in clean environments, among other advantages.
Based on the frameless and integrated direct drive rotary motor, a new modular direct drive rotary motor has been developed.
Modular direct drive rotary motor
A key challenge with most direct-drive rotary motors is that applying enclosed or frameless direct-drive rotary solutions to traditional servo motor systems can lead to increased costs. To address this challenge, a new direct-drive option technology has emerged. This new technology, called modular direct-drive rotary, combines the performance of frameless direct-drive rotary motors with the ease of installation of full-frame motors.
Modular direct-drive rotary motors represent a novel direct-drive solution. Their structure includes a unique bearingless housing with an integrated rotor, stator, and factory-aligned high-resolution feedback unit. The application of cylindrical direct-drive rotary motor technology eliminates mechanical transmission components, retaining all the advantages of direct drive while avoiding the complexity and cost of traditional enclosed or frameless direct-drive rotary motor solutions. Modular direct-drive rotary motors utilize a novel compression coupling to connect the rotor to the shaft, and include a unique chuck design, enabling "plug and play" operation in under 30 minutes.
The advantages of modular technology, along with its competitive pricing and significant reduction in total lifecycle costs, will accelerate the application of direct drive technology in the design of new machines in many fields, such as metallurgy, packaging, printing, semiconductors, and factory automation.
Most mainstream collaborative robots today adopt a modular joint design, using direct-drive motors and harmonic reducers. The internal structure of each joint is basically the same, only the size varies. For example, each axis of the iiwa is basically like the image below:
Each joint contains a motor, servo drive, harmonic reducer, motor-end encoder, joint-end position sensor and torque sensor, with the motor and reducer directly connected.
Collaborative robots will become the mainstream robots of the future, and they need to meet the needs of the main customers in the emerging robot market—small and medium-sized enterprises. When humans work together with collaborative robots, safety is one of the primary considerations. Safety means low kinetic energy. To reduce the kinetic energy of the robot during movement, collaborative robots need to be lighter and have a simpler structure.
In small robotic arms, frameless direct drive motors are typically used to reduce the size of the robot joints, lighten the robot's weight, and improve its motion efficiency. However, using direct drive motors also brings a new challenge: higher technical implementation difficulty and application integration costs.
This is partly due to the complex operation and usage of frameless motors themselves, and partly because the design and manufacture of robots requires integrating multiple disparate motion control and transmission components, such as torque motors, encoder feedback, brakes, and harmonic reducers, into the extremely limited space of the robot joint, while simultaneously ensuring the robotic arm's fast, flexible, and reliable motion performance. The resulting extremely long development cycles and high manufacturing costs have, to some extent, hindered the widespread application and adoption of small-jointed robots.
This leads to the next product we'll be introducing – the robot joint module.
Robot joint module
This robot joint module, named RGM, is a new product released by Kollmorgen last year and was first showcased at the CIROS China Robot Exhibition.
The RGM is only about the size of a fist. Viewed from the side, its frame is T-shaped. Below is the module's flange base, used to mount it to the end of the previous robotic arm. On the left is the motor end cover, and on the right is the motor shaft output, connecting to the next robotic arm.
This RGM integrates multiple core robot joint components, including servo drives, frameless direct drive motors, harmonic reducers, feedback encoders, and brakes, into a single modular assembly. It is designed and packaged to fit the 90° rotation angle of the robot joint, allowing it to be used directly as a complete joint assembly on the robotic arm of an industrial robot.
This means that when designing and manufacturing robots, users do not need to consider complex robotic arm joint connections and power integration. They can directly use RGM joint modules to connect and drive the robotic arm, thereby saving a series of complex steps and processes such as the design, installation, integration and testing of a large number of scattered components. In particular, there is no need to spend a lot of time on the use of frameless torque motors.
In terms of power configuration, since each joint module integrates a motor driver, uses a 48V DC power supply and a CANopen control bus, if RGM joint modules are used, there is no need to equip each joint axis of the robot with a separate servo driver; only a robot motion controller with an integrated CANopen bus is needed. This will save a significant amount of electrical cabinet installation space, making the equipment system more compact.
Looking at the electrical connections, because the power and communication ports of multiple joint modules can be connected serially in a chain topology, and RGM uses hollow shaft frameless motors and harmonic reducers, the electrical cables of the robot arm integrating RGM joint modules can be directly connected in series inside the robot arm cavity, instead of being hung side-by-side on the surface of the robot arm as in traditional robots. This not only makes the robot's appearance much simpler, but more importantly, because there are no twists and turns of multiple parallel cables at the joints, the motion load during robot operation is reduced. At the same time, fewer cables will also reduce the weight of the robot arm, all of which contribute to improving the robot's working efficiency.
The RGM employs 19-bit Biss feedback, achieving a repeatability accuracy of 0.001°. Simultaneously, the RGM has an encoder at both the input and output ends. By comparing the position and speed feedback from the two encoders, and referring to the output of the drive current and motor torque, the magnitude of the external force acting on the joint of the module can be determined. Feeding this data back to the controller allows for convenient and safe control of the robot without the need for additional auxiliary sensors.
Therefore, by integrating multiple disparate robotic arm joint components into a single integrated module, RGM essentially provides a one-stop solution for robot joints. This integrated modular joint component has the potential to fundamentally change the manufacturing process of industrial robots. Compared to traditional robot manufacturing methods, using RGM's integrated joint modules will greatly simplify the power integration of robot joints and lower the barriers to development and application of industrial robots. This allows robot manufacturers to focus more on developing their robot's application scenarios rather than getting bogged down in complex power mechanical components.
