Tesla’s humanoid robot Optimus uses 1:14 planetary roller screws. At Tesla AI Day on October 1, the humanoid Optimus prototype used planetary roller screws and harmonic reducers as an optional linear joint solution. According to the rendering on the official website, an Optimus prototype uses 14 harmonic reducers and 14 planetary roller screws. The planetary roller screws have attracted widespread attention in the market as the transmission unit design that exceeded expectations for this launch.
Figure 1: Optimus with planetary roller screw as an option
The new generation of linear drive branches, planetary roller screws, are already being used in high precision fields worldwide, combining helical and planetary movements with high overall performance requirements. Compared to ball screws of the same size, planetary roller screws are characterised by “heavy duty, high efficiency, high speed and long life” and have been used on a large scale in overseas military and high-end civil markets. Planetary roller screws are used in aerospace, weaponry, nuclear power and other special applications. For example, aircraft landing gear, helicopter suspension launchers, etc. In addition, there is demand for machine tools, automotive ABS systems, petrochemicals and other applications in the civil market. According to statistics, in 2021 the global planetary roller screw 230 million U.S. dollars, the next five years compound growth rate of 5.7%, humanoid robot or inject more possibilities for the industry.
Market space: global estimate of US$330 million by 2025, future may be full of more possibilities
Global planetary roller screw penetration continues to expand:
► For ball screw replacement: no ball returner required, circumventing noise issues. In addition, planetary roller screws have more points of engagement, providing better stiffness and load carrying capacity in harsh operating conditions. In machine tools and other fields, planetary roller screws are constantly in favour due to their smaller lead lengths and higher loads; in robots, automation and other electric cylinders, they are gradually adopted due to their fast response, etc.
► Alternative to hydraulic transmission: hydraulic transmission requires hydraulic pumps and valves, etc. With the adoption of planetary roller screws, the total volume is reduced, oil leakage problems are circumvented and disassembly and maintenance are simple. In the field of construction machinery, through the planetary roller screw to replace the large load hydraulic system, can effectively realize the electronic control, easy to replace. In the field of new energy vehicles, hydraulic brakes are replaced by electro-mechanical braking systems (EMB) for faster response.
According to Persistence market research, the global planetary roller screw market is expected to grow at a CAGR of 4.8% to US$230 million from 2012 to 2020, or approximately RMB 1.52 billion. From 2020 onwards, with increasing demand for new energy sources, Persistence market research expects the market to grow at a CAGR of 5.7% from 2020 to 2025 to reach US$330 million, or approximately RMB 2.01 billion.
In response to different application environments, four additional types of factions of global planetary roller screw construction have been derived from the standard type:
► Reverse type: nut as active member, screw as output member, no internal gear ring. The great advantage is the compactness and the use in small stroke work scenarios.
► Recirculating: the inner ring is removed and the return (cam ring construction) is added, the roller can rotate inside the nut for one week and then return to its position. By increasing the number of threads, it has a higher stiffness capacity and is used in medical devices, optical precision instruments, etc.
► Bearing ring type: increase the shell, end cover, cylindrical roller bearings and other components, greatly improve the load capacity, used in heavy machinery, petrochemical and other fields, manufacturing costs are high.
► Differential type: the roller is segmented ring groove structure, remove the inner gear ring, applicable to the transmission of larger occasions. But in the process of movement, the threads will slide, easy to wear in the case of large load.
The USA is currently the largest demand country for planetary roller screws worldwide, followed by Germany and the UK, with the three regions together accounting for 50% of the overall market. Tesla is looking forward to a million humanoid robots, or bring more possibilities. 2022 Tesla AI Day, Musk hopes to achieve large-scale sales of humanoid robots within 3-5 years, we believe that humanoid robots are expected to inject windfall for the industrialization of planetary roller screws.
Post time: May-26-2023
