Piezo motors meet mechanical engineering trends
High-precision, reproducible movements in the nanometer range are just as important in focusing and scanning applications as in alignment and measuring tasks. Miniature piezoelectric motors from the Swedish company PiezoMotor feature precision movements with zero backlash that cannot be achieved with other motion technologies.
Design-related gaps between the single motor and drive components cause backlash, which is needed for some applications: The advantages for the single components are free movement, easy assembly, elimination of strain, and immunity to temperature fluctuations and contamination. But mechanical backlash also reduces positional accuracy and increases wear – which is undesirable in certain biological and medical engineering applications, the semiconductor industry, and applications that use particle accelerators or digital scanners. These negative effects are counteracted by miniaturized motors from the Swedish company PiezoMotor.
Today’s motor manufacturers are increasingly confronted with the challenges of combining zero backlash with maximum precision and miniaturization. Constantly increasing requirements for precision in production necessitate the development of precision machines and high-precision analytical instruments. Since they eliminate both the drive train and friction losses, direct drives are often used to meet these requirements. The advantage of direct drives is not only the boost in overall efficiency, but also the elimination of imprecise movements due to backlash in the gears. Direct drives are much more dynamic than conventional drives – resulting in shorter reaction times, higher path accuracy and faster final speeds or rotational speeds.
The LL06 with backlash-free direct drive and with the weight of only 16 grams is the smallest motor from PiezoMotor
Self-locking, with zero backlash
The design of classic direct drive systems is simple and compact. What direct drive electric motors are lacking, however, is the capability of self-locking, which in many applications necessitates the use of brakes and also affects the size. A piezo motor does not have these problems. Piezoelectric motors from the Swedish manufacturer PiezoMotor are therefore used in all applications requiring maximum precision and miniaturization. The properties of piezo technology make it attractive for numerous applications. The robust, high-precision linear and rotational motors use the patented Piezo LEGS® technology for back-lash free movement in the nanometer and even sub-nanometer range.
Piezo LEGS® technology takes advantage of the so-called inverse piezoelectric effect. Piezoelectricity describes the change in the electric polarization of solid bodies when they undergo elastic deformation – conversely, it causes deformation of materials when voltage is applied. Piezo LEGS® are ceramic legs that can be lengthened as well as laterally curved by voltage, causing them to move. Synchronisation of the legs, which are arranged in pairs, causes a movement in the sub-micron to nanometer range, which drives the linear and rotational motors.
The movement of the ceramic legs is achieved by applying an electric voltage. The elements are raised and lowered in pairs to push the rod in the requested direction
Minimal dimensions, maximum power
The rod in the motor is in direct contact with the moving object and the piezo elements in the motor. The frictional coupling between the legs and the rod results in zero backlash, an extremely short reaction time and a high resolution. In addition, the direct drive enables powerful locking with no power consumption when stopped, since locking and driving are performed by the same actuators. Without direct contact the tips of the legs would execute an elliptical movement, but instead they bear down on the rod and push it in the desired direction. The phase-shifted movement of the actuators always locks the rotor or the rod, so that it is never free-wheeling.
Their enormous miniaturization is another advantage of piezo motors, which makes them a good alternative to conventional micro motors for measuring instruments, medical devices or microscopes.
The force of a Piezo LEGS® motor depends on the volume of the piezo material used in the legs and can be scaled from a few newtons to several hundred newtons. PiezoMotor manufactures Piezo LEGS® elements consisting of four or six legs, to provide a portfolio of products with different stall force.
The LS15 linear motor can be easily mounted on the side of a linear stage. In the center you can see the legs touching the rod.
Zero backlash in the smallest space
Compared to conventional solutions, the number of parts and elements in a piezo motor is kept to a minimum: The simplicity of the electronic drive components saves space, allowing a high degree of miniaturization in every application. Zero backlash, high holding force in power-off, and excellent dynamics and miniaturization capabilities are convincing advantages for many users. The low-maintenance design and vacuum compatibility of piezo motors make them attractive for a large range of OEM applications with a focus on high-precision positioning.