Serial Kinematic 18dof

Video example: LINK

 

The articulated arm prototype 18-dof designed to Salpo srl aims to move a tool in the space quickly and silently and simultaneously to attenuate vibrations and harshness typical of anthropomorphic solutions. The structure is currently composed of 18 plates serially hinged with 17 bounds and rotated to cover the whole space of angles. It is immediately evident that having 18 degrees of freedom the space of positions reaches an order of magnitude overabundant, this superabundance of states results in a greater freedom of choice on the policy of trajectories construction. This means it permits to reduce the moments of inertia thus obtaining a further efficiency. On the other hand this is the standard mode of management and execution of movement in nature, even because the surplus of degrees of freedom allows a substantial margin of recovery in case of unforeseen events. The simplified model of the system consists of two related parts:

  • Calculation and correlation of the trajectories of each joint
  • Trajectories execution

The calculation of the trajectories is the part computationally heavier, but at the same time the one that takes more advantage by the rapid evolution of the calculation units. Thanks to a mathematical model that describes the inverse dynamics of the structure, the movement of the arm is split into the movements of each single axis, optimized according to the requirements (inertia, speed, dynamic ...) and then stored for execution. The processing can be performed either in off-line mode, (cyclical trajectories) both in real-time mode associated with a feedback from the system as a camera, sensors, etc.. .The second phase, the execution, is completely dependent on the motion control system LUVA (Logic Array for Value Unit). The control system independently manages all 18 axes both in synchronous and asynchronous mode, working directly at the micro-step level. Described features make the system and its future developments ideal for applications with lightweight tools on complex surfaces: laser welding, coating, adhesive deposition, water jet cutting applications in addition to the typical anthropomorphic application. It has been hypothesised a working mode in which the addition of a sensor or a camera in the proximity of the end-effector can be used as a feedback to the control system, it allows to obtain an high-precision positioning even in situations such as not stable systems (eg pipes suspended). The technology, revisited in size and materials but not in the concept, lends itself to very complex applications, such as medical applications or applications in hostile environments (sewers, subsea installations, mines ...). This is possible above all thanks to the LUVA controller features: high accuracy, high number of axles, speed, low computational load, to real-time / off-line mode.  it is the ideal solution for working on parallel kinematics being able to make the most of exploiting scalability, power and flexibility of current workstations.