New intelligent power-assist systems based on differential transmission

Abstract

This paper presents a novel Cobotic system with differential CVT. The new system is significantly cheaper, simpler to control and more efficient than Cobots with S-CVTs. Both path-guidance and power-assist functions can be simply realized with the new system. Basic structures, kinematic and dynamic models, as well as control algorithms, which are essential for design, control synthesis and control of the system, are briefly presented in the paper

Free Kinematic Singularity Controller for a Planetary Gear Based Cobot

“…In general, for fully actuated robots, synchronization of the motors to get a movement of the endpoint is advisable, nevertheless, in cobotic systems, motors are not used to actuate the joints of the system, while the endpoint trajectory control is achieved via the joint velocities [3,4]. There exist different ways to control cobots [18][19][20], however, most of the cobot controls are based on the cobot kinetic relation between link velocities and joint velocities, the so called Jacobian, such that they are affected by singularities on this Jacobian.…”

“…In such conditions, the robots must adapt to changing and uncertain conditions, which implies providing the robot with multiple sensors and more sophisticated control schemes [1]. One way to deal with robot applications in unstructured environments is by introducing a human in the loop, such that the human provides the robot with the skill to take fast decisions and to adapt to the environment, this idea gives rise to the so called collaborative robots (cobots), which are nonholonomic passive systems entitled to interact with human operators [2][3][4]. Automotive industry [3], surgery [5], training devices [2] and rehabilitation [6] are some applications where cobots have been used.…”

“…In a cobotic system, the system perfomance depends on a shared control, where the human operator exerts the whole movement force and the cobot provides a virtual guiding surface. Virtual guiding surfaces are implemented by means of continuously variable transmissions (CVT) that constrain the velocity rate among the joints of the kinematic chain [4]. There exist different kinds of CVT, for example the passively adaptative rotary-to-linear CVT [8], nevertheless, for cobotic systems, the spherical CVT and the CVT based on differential gear trains are the most used [3,4].…”

“…By activating the control system (drive motor), the transmission rate in the CVT can be controlled, implying that a desired path can be imposed. That is, cobots are passive devices where the human operator supplies the force to the system to perform the entrusted task [3,4].…”

Modelling and experimental validation of a planar 2-dof cobot as a differential-algebraic equation system

“…The spherical CVT and the CVT based on differential gear trains are the most used CVTs in cobots [6,8], nevertheless, other kinds of CVTs can be used for applications in cobotic systems. An example is the passively adaptive rotary-to-linear CVT [13], which can be used in a pick and place cobotic system, without the need of additional mechanical components to convert the rotational movement into linear movement.…”