Robot Joint Actuators

What a joint actuator is

An actuator is the complete moving joint: a motor, a reducer or screw, an encoder, a driver and often a brake or torque sensor, built into one housing. Tuopu describes the two main types as linear and rotary, and says humanoids need dozens of them, which must be light, small and low-power while integrating all of those parts (2026 interim report, p. 12).

The parts are covered on their own pages: the servo or frameless motor, the harmonic reducer for rotary joints and the planetary roller screw for linear ones. At Tesla AI Day 2022, Tesla showed this stack in its Optimus rotary actuator, which combines a bespoke permanent-magnet motor, a clutch, an output bearing and a strain wave gear.

The engineering argument for buying an actuator rather than the parts is integration: fewer interfaces, lower weight and one supplier responsible for the joint. The cost is that the buyer depends on that supplier for the most important component of the robot.

Where China stands

The filings show two groups of suppliers.

Motion-control companies that already sell integrated units.

• Zhongda Leader (中大力德, 002896.SZ) reported ¥252.9m of integrated actuator unit revenue in the first half of 2026, at a 22.5% gross margin, down 4.6 points. Its customers are in logistics, machine tools, packaging and other industries as well as robots (2026 interim report, pp. 9, 11). Its board has approved a placement of up to ¥530m, with ¥250m towards a joint module project for embodied-AI robots (placement plan, pp. 4, 15-16).
• Leaderdrive (绿的谐波, 688017.SH) sold 12,178 sets of mechatronic products in 2025, up 72%, and ¥54.7m of them in the first half of 2026 (2025 annual report, corrected, p. 38; 2026 interim report, p. 145).
• Inovance (汇川技术, 300124.SZ) supplies joint modules, frameless motors and bionic arms, and says it has begun sampling to humanoid makers (2026 interim report, p. 25). Kinco (步科股份, 688160.SH) sold 68,000 integrated i-Kinco servo modules in the first half of 2026, a line it develops mainly for mobile robots (2026 interim report, pp. 15, 16).

Auto-parts groups entering robots.

• Tuopu's robot actuators earned ¥14.0m in the first half of 2026, up 83.4%, at a 27.0% gross margin, and have reached small-batch delivery (2026 interim report, pp. 8, 12).
• Sanhua (三花智控, 002050.SZ) says its robot electromechanical actuators are in batch delivery and line ramp-up, but gives no revenue, volume or customer (2026 interim report, p. 13).

The only humanoid maker any of these filings names as a customer is AgiBot, which Zhongda Leader lists among its end customers without saying which products it buys (2026 interim report, p. 9). Media reports name Tesla for Tuopu and Sanhua; see below.

What the media say about Tesla

Neither Tuopu's nor Sanhua's filing names a customer, but Chinese media have linked both to Tesla's Optimus humanoid. These reports are unconfirmed and should be read as such.

• On 17 September 2026 the 21st Century Business Herald, citing industry sources, reported that a Tesla team had begun a new round of factory audits in Ningbo aimed at Optimus mass production, with orders already placed with suppliers. Tesla did not respond (IT之家, reprinted 19 September 2026).
• In the same report, a Tuopu staff member said by phone that it had no notice of an audit, but that it and Tesla cooperate on linear, rotary and dexterous-hand actuators and that its robot parts base was ready. A Sanhua staff member said they were not aware of the audit, and that the company is working with a major customer on robot joint actuators.
• In October 2025 a rumour that Tesla had placed a US$685m order with Sanhua for linear actuators drove its shares up sharply. Sanhua published a clarification the same day saying the rumour was untrue and that it had no undisclosed material matters (IT之家, 15 October 2025).

Accounts differ on which company makes which actuator type, so we do not state a split. The staff replies are phone answers to a reporter, not company announcements.

Margins

The margins on offer differ. Tuopu's actuator business earned 27.0%, against 16% to 21% for its car parts (pp. 8, 12). Zhongda Leader's integrated actuator units earned 22.5%, and the margin fell 4.6 points in a year. The figures are not like for like: Tuopu's is a very small base, while Zhongda Leader's units go to customers across industry as well as robots.

Our view: the integrated actuator revenue that is large today sits with motion-control companies selling to industry, not with the auto-parts groups. The car-parts groups bring manufacturing scale and capital, but their own filings show robot revenue that is still a rounding error. The likelier test of who wins is price and margin once humanoid orders are in the thousands, not whose design is better.

What to watch

• Named customers. Beyond AgiBot's listing as a Zhongda Leader end customer, no filing names a humanoid maker as an actuator customer. A filing that confirms the media reports on Tesla, or says which products AgiBot buys, would be the first hard evidence of share.
• Margin as volume arrives. Zhongda Leader's margin on integrated units fell 4.6 points in a year, while Tuopu's 27.0% is on a very small base.
• Capacity. Zhongda Leader's placement and Tuopu's robot parts base, whose first phase is largely complete, will show whether suppliers are building ahead of orders.
• Parts makers integrating upward. Leaderdrive and Inovance already sell modules, which could squeeze the actuator makers that buy their parts.