Conventional robotic actuators use a very traditional design of electric motors and gear systems to make robots move. These geared systems suffer from many limitations: Low speed, which limits productivity; play between the gears (known as backlash) which limits precision; high inertia that prevents rapid safety stops; high backdrive friction, which (with high inertia) makes gear systems more fragile and prone to damage during unexpected or intentional impact
Genesis breakthrough in the form of direct-drive actuator for robotic joints
The LiveDrive direct-drive actuator from Genesis Robotics is a radical departure from conventional actuator design. It is well known among roboticists that a direct drive motor would be the ideal actuator, but conventional direct-drive motors lack the necessary torque. Improvements in conventional direct-drive motors of 10 to 20% are rare. The three foundational discoveries of the LiveDrive break this mold by providing over three times greater torque than a conventional direct drive motor.
Three technologies are at core of actuator innovation
- Amplified magnetics — LiveDrive takes the strongest magnets in the world, and nearly doubles their effective force.
- Structural-magnetic synergy — The tremendous magnetic forces produced by the LiveDrive would collapse a conventional motor construction. The LiveDrive combines a new level of magnetic performance, with the structural rigidity to withstand the resulting forces.
- Thermodynamic anomaly — Heat is a limiting factor in any electromagnetic device. The combination of the first two foundational discoveries provides a level of heat dissipation that allows the LiveDrive to operate at much higher power levels than a conventional motor.
Specifications of the Genesis Robotics actuator:
Repeatability 0.2 arc-sec; Torque to inertia 2,213 Nm/kg·m
Top speed is 400 rpm; Outer diameter of 269 mm; Inner diameter of 80 mm; Axial thickness of 16 mm
Continuous torque to 54 Nm; Peak torque of 120 Nm
Mass 5.1 kg and power density 976 kW/m; Cooling through forced air
When all three discoveries are combined, the result is a revolutionary advance in robotics. All the benefits of a direct drive motor are achieved at a level of torque that allows the LiveDrive to be used directly in the joints of a robot, without the need for a gearbox.
Actuator aims to be fast, safe, and versatile Never has this level of speed, torque, and precision been combined in a device with the simplicity to allow low cost manufacturing and ease of implementation.
The result is remarkably higher speed combined with the ability to stop fast enough for safe operation around humans. Genesis Robotics and LiveDrive is changing the robotics industry, helping to build the fastest, safest and most versatile robots available. Visit the manufacturer at genesis-robotics.com.
Howard Havlicsek says
March 20, 2018 at 11:42 amIn the infantsy of articulated robots, direct drive was seen as the prefered mode of joint actuation (first accomplished with hydraulic actuators). One school of thought is that a direct drive linearizes torque production and ensures smooth joint motion. This may solve the problems of backlash, slip-stick friction, back drive capability, etc. But what about these following issues?
1. Gravity becomes a significant factor in robot control, especially as it relates to startup and shutdown.
2. Control of a direct drive arm is much more challenging due to coupling between the linkages/joints.
3. Geared robot joints have finite stiffness due to mechanical compliance and generally results in a trade-off of accuracy, motion dynamics and cost. High joint stiffness in direct drive robots is only achievable if a high bandwidth can be achieved. This is usually only possible when the control system incorporates decoupling of the joints.