# How a Robot Actuator Controls Force and Speed with Gears > This patent describes a compact robot actuator that uses a special gear system and two motors with different electrical resistance to precisely control both the force and speed applied to a robotic arm or tool. - **Patent:** US 8209052 - **Original title:** High performance differential actuator for robotic interaction tasks - **Owner:** Societe de Commercialisation des Produits de la Recherche Appliquee SOCPRA - **Granted:** 2012 - **Status:** Active - **Times cited:** 5 - **Field:** robotics, mechanical, automation, consumer_electronics, medical_devices ## What it does The patent details a "mechanical differential actuator" (Claim 1) designed for interacting with a "mechanical load." It uses a "mechanical differential" (like a special gearbox) with three connection points, called "interaction ports." A "first transducer" (like a motor or brake) with "low impedance" connects to one port, mainly controlling force (Claim 4). A "second transducer" (like another motor) with "high impedance" connects to a second port, mainly controlling speed (Claim 10). The third port connects to the "load," which is what the robot needs to move or apply force to. The clever part is that the second transducer's high impedance is so large that it "does not influence significantly" the overall behavior of the actuator (Claim 1), allowing for independent and precise control of both force and speed at the load. For example, a robot arm could use this to gently pick up a delicate object while also moving it quickly and precisely. ## What it does NOT cover - Does not cover actuators that lack a mechanical differential with three distinct interaction ports. - Does not cover systems where the second transducer's impedance significantly affects the overall equivalent impedance of the actuator (Claim 1). - Does not cover actuators where the first transducer is not primarily a source of force or the second transducer is not primarily a source of speed, as described (Claims 4, 10). - Does not cover purely electronic or hydraulic control systems that do not incorporate a mechanical differential. - Does not cover actuators that cannot control both force and speed at the load. - Does not cover systems where the mechanical differential is not compact or cannot transfer large forces relative to its volume. ## The clever bit The novelty lies in combining a mechanical differential with two transducers having vastly different impedances. Specifically, the second transducer's high impedance is engineered to be so large that it isolates the overall actuator's behavior from its own, allowing for independent and precise control of both force and speed at the output load, all within a compact design. ## Real-world examples 1. Collaborative robot arms (cobots) 2. Surgical robots 3. Haptic feedback devices 4. Industrial automation manipulators 5. Exoskeletons for assistance or rehabilitation ## Why it matters This technology is important for creating more advanced and versatile robots. By allowing precise control over both force and speed in a compact design, it enables robots to perform delicate tasks, interact safely with humans, and operate efficiently in tight spaces. This is crucial for applications ranging from manufacturing to medical robotics. ## Frequently asked questions ### What does How a Robot Actuator Controls Force and Speed with Gears cover? This patent describes a compact robot actuator that uses a special gear system and two motors with different electrical resistance to precisely control both the force and speed applied to a robotic arm or tool. ### Who owns patent US 8209052? Societe de Commercialisation des Produits de la Recherche Appliquee SOCPRA owns this patent, granted in 2012. ### When does this patent expire? This patent is expected to expire on March 30, 2027, when the invention enters the public domain. ### What is patent US 8209052 cited by? This patent has been cited by 5 later patents that build on its ideas. ### What problem does this patent solve? This technology is important for creating more advanced and versatile robots. By allowing precise control over both force and speed in a compact design, it enables robots to perform delicate tasks, interact safely with humans, and operate efficiently in tight spaces. This is crucial for applications ranging from manufacturing to medical robotics. ### What does this patent NOT cover? Does not cover actuators that lack a mechanical differential with three distinct interaction ports. **Full plain-English explainer:** https://patentbrief.org/patent/us/8209052/high-performance-differential-actuator-for-robotic-interaction-tasks **Original patent:** https://patents.google.com/patent/US8209052 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [Uniform Scaling of Haptic Forces in Surgical Systems](https://patentbrief.org/patent/us/12114954/uniform-scaling-of-haptic-actuators) — This patent describes a surgical system that uses a single scaling factor to adjust the strength of touch feedback from multiple motors, ensuring the feedback feels consistent even when one motor reaches its maximum power. - [How a Robotic Exoskeleton Helps Your Shoulder Move](https://patentbrief.org/patent/us/10800031/spherical-parallel-manipulator-architecture-for-shoulder-robotic-exoskeleton) — This patent describes a robotic shoulder exoskeleton using multiple straight-moving actuators arranged in a "spherical parallel manipulator" to assist or rehabilitate arm movements while preventing joint misalignment. - [How a Robotic Surgical Tool Clamps Tissue Manually and Automatically](https://patentbrief.org/patent/us/11786761/ultrasonic-robotic-tool-actuation) — This patent describes a surgical tool for robotic operations that can clamp tissue using a motor-driven yoke, but also allows a surgeon to manually control the clamping action. - [How a Surgical Robot Arm's Wrist Moves Instruments](https://patentbrief.org/patent/us/12414825/surgical-arm) — This patent describes a specific design for the end part of a surgical robot arm, called the terminal portion, which uses a clever arrangement of three joints to precisely position and rotate surgical tools. - [Robots That Don't Get Stuck: A Master-Slave Control System](https://patentbrief.org/patent/us/9855653/master-slave-system) — This patent describes a robot control system where a human-operated 'master' robot guides a 'slave' robot, preventing either from getting into awkward, uncontrollable positions by carefully planning the master robot's movements.