An eye on efficiency

A conventional eye test is a time consuming process that depends on the operator’s experience and ability, as well as the patient’s subjective assessment as to whether one lens improves their sight better than another. The L80+ automatic diagnostic device from Israeli company Visionix, can perform comprehensive diagnostics to the human eye, both the optics and the cornea. The L80+ provides absolute and objective data within few seconds, with a fully automatic process that has almost no need for operator intervention. The device automatically recognises the patient’s eye, centring the optical head in front of it, focusing on the eye’s optics, then measuring the eye. It then moves to the second eye and performs the same sequence. The L80 can be used by eye doctors and by opticians for prescribing the client’s lenses. Since the measurement data will be used as the basis for corrective measures, the standard for the precision of the device has been set high. To meet this high standard, Visionix uses stepper motors and brushless dc motors for the movements of the chin rest and of the laser. The control of all six axes required for these movements is provided by a single module – the TMCM-VI-802 – developed specifically for this purpose by Trinamic Motion Control. The control of five stepper motor axes and one BLDC-axis was combined on one board. Three of the stepper motor axes are low power, driving motors with phase currents up to 1A. The other two axes are suitable for motors with phase currents up to 2A. According to TRINAMIC sales manager Guido Gandolfo, this project is a typical example of the economic viability of a customer specific solution based on optimising a standard solution. The development of the eye diagnostic device required five stepper motors and one brushless dc (bldc) motor. Standard solutions were used initially in the prototype: the TMCM-610, a six axes standard board, and the TMCM-170BLDC module. The latter is a round, double stacked board that can be placed directly on the motor. However, this feature was not used by Visionix, hence the idea of optimising the device in terms of production and of combining the control of the axes on one board. Direct links between the customer, its Israeli distributor and Trinamic helped in this process, since development of the customer specific solution ran in parallel to pre production of standard products. As is usual in such cases, standard products were used in the prototype and in pre production in order to migrate to a cost effective, optimised solution for the series production. The special feature of the solution is the combination of the stepper and bdlc motor control system on one board. One processor is available for each motor type, and all connections and wiring need only to be done once. This reduces costs, effort and sources of error. And it is in this integration expertise that Gandolfo sees future potential: since the parameters always need to be adjusted, multi axis boards will always remain individually programmable solutions that offer a wider range of models, in terms of the high and low power axes, or the number and types of motors. Switching to modular components would not be good for production, since some assembly steps and components would have to be provided twice. Individual elements, such as low and high power axes or bldc controls, are not developed from scratch: the solution is made up from individual blocks. All that is needed is for the software to be adapted to the new layout. This type of reengineering or redesign is affordable and quick to implement.