FEATURE Robotics
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Motion performance and durability for high-dexterity robot builds
O
ne of the key functions of humanoid robots in industrial applications is to improve effi ciency and safety whilst
performing tasks in environments that are arduous or even dangerous, yet require utmost precision in every action. To achieve a high level of robotic dexterity and precision, multiple motor axes are required. Humanoid robots need more than 20 motor axes to actuate human- like movements, each axis representing a degree of freedom in movement, such as rotation or translation. Alternatively, cobots usually have six to eight motor axes, controlling each robotic joint for movement and positioning in the shoulder, arm and wrist, as well as end eff ectors, such as grippers.
Ensuring dexterity and control A Chinese manufacturer of humanoid robots and cobots approached Portescap to provide a motion solution to drive and control the arm and knee joints of several of its designs. The requirements for motion performance were high, in order to achieve the necessary speed and accuracy of motion. This would ensure dexterity as well as control establish safety when working in proximity to humans. With many axes involved, cost-eff ective manufacture was also a priority for the robot maker.
Both cobot and humanoid robot designs had highly-defined physical footprints and would also need to minimise mass to optimise overall dexterity and movement efficiency. Additionally, the motion solution had to fit within a compact, low-weight envelope. Moreover, working alongside humans, the robot noise levels had to minimal, so the motors driving them must offer quiet operation.
Minimising weight and footprint The OEM engaged Portescap based on its extensive experience in designing motion solutions for robotics. The motion solution designer specified its Athlonix 24DCT brush DC motor and MR2 encoder to meet the OEM’s requirements.
18 September 2023 | Automation
Neodymium magnets increased the available torque by 20% over the competing motor designs, thanks to the properties of greater magnetic strength, which also enhanced power density. The motor’s coreless design, free from a traditional iron core but instead utilising surrounding permanent magnets, also contributed to a lower mass motion package. To optimise the motors’ lifetime, Portescap’s solution included constant spring force carbon brushes. This design ensured that regular contact with the commutator minimises the potential of bounce and increases friction during operation, as well as improves performance with a more consistent electrical connection. The smooth performance would also reduce both audible and electrical noise, which is crucial when operating in environments alongside other electronic equipment.
Motion solution customisation Accurate position control for the robotic joints was achieved with a Portescap MR2 magneto-resistive encoder. Using a resistive element to measure position, accurate feedback with up to 512 lines of resolution could be provided. Meanwhile, the resistive design gave inherent
Portescap worked with a robot maker in China to optimise motion performance and durability, whilst ensuring cost- effective production
durability, even in harsh operating environments, thanks to its free-of- moving-parts design, as well as protection with Portescap’s sealed housing. To achieve the robot manufacturer’s cost
targets, Portescap tapped into its global supply chain to source the most cost- optimal components whilst still meeting the necessary performance criteria. Portescap’s engineers were also able to collaborate closely with the robot OEM’s design team throughout the project. This process enabled the customisation required to achieve the specifi cation, whilst meeting the tight timescales for development and minimising cost of production.
Portescap’s MR2 magneto-resistive encoder helped to achieve accurate position control for the robotic joints
CONTACT:
Portescap
www.portescap.com
automationmagazine.co.uk
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