An innovative design for electric torque motors that could reshape how heavy-duty machinery, industrial automation, and electric vehicles are built is reported in the International Journal of Hydromechatronics. By rethinking how permanent magnets are embedded within the rotating component responsible for generating motion, the researchers have developed a method that increases torque without compromising durability or thermal stability.
Torque motors are a category of electric motor engineered specifically to generate high levels of torque, or rotational force, particularly at low speeds. This makes them ideal for applications such as hydraulic pumps, industrial robotics, and aerospace actuators. Unlike conventional motors that require gearboxes to achieve sufficient torque, torque motors often use a direct-drive approach, eliminating mechanical complexity and potential points of failure. However, enhancing torque output without risking overheating or structural failure remains a central engineering challenge.
Traditional torque motor designs commonly mount permanent magnets directly on the surface of the rotor. While this arrangement can strengthen the motor’s magnetic field and thereby improve torque, it introduces a serious vulnerability: magnets can detach under stress, particularly at high rotational speeds or under heavy loads. To mitigate against this, engineers commonly use carbon fibre sleeves to encase the magnets. But these protective layers increase the electromagnetic air gap, i.e. the space between rotor and stator where magnetic interaction occurs, and this reduces magnetic efficiency and so the torque.
This research focuses on a novel semi-inset permanent magnet pole rotor structure. Such a design offers a more integrated solution by partially embedding the magnets into notched sections of the rotor itself, the new structure locks the magnets securely in place reducing the risk of detachment without the need for bulky external reinforcement. The approach allows the electromagnetic air gap to remain tight. In turn, this supports a stronger magnetic flux for greater torque generation.
The team has simulated their design using Finite Element Analysis (FEA), a computational modelling technique that factors in physical forces, stress, and heat. Such simulations allow for the fine-tuning of the magnet shape and position to optimize magnetic flux density and structural integrity. Particular attention was paid to the thermal characteristics of the motor, since greater torque typically demands more current, and thus produces more heat. Heat dissipation features were integrated to prevent overheating, and mechanical tests showed the structure could endure operational stress without magnet failure or demagnetization.
He, X., Xiang, P., Xu, Z., Wei, X. and Li, Y. (2025) ‘Development of a torque motor with enhanced performance employing novel semi-inset PM pole’, Int. J. Hydromechatronics, Vol. 8, No. 5, pp.40–54.
Footnote
The word torque, meaning a twisting or rotational force derives from the Latin verb torquere “to twist”, but also to distort or to torture. The Latin word derives from the proto-Indo European (PIE) root *terkw-.