A linear actuator includes a planetary gear system includes a sun gear, a ring gear, and a planet carrier. A linear output mechanism is coupled to the planetary gear system. A first motor is configured to drive a first input shaft, and the first input shaft is coupled to the planet carrier. A second motor is configured to drive a second input shaft, and the second input shaft is coupled to the ring gear. A first brake is coupled to the first motor and is configured to be engaged into a braked position that holds the planet carrier fixed. In the braked position, rotation of the ring gear results in rotation of the sun gear for linear displacement of the linear output mechanism.

A pneumatic stepper motor includes a housing, said housing accommodating at least part of: a rack or geared axle comprising a plurality of gear elements; and two pistons, each comprising at least two teeth, said pistons being arranged to cooperate with said rack or geared axle. The racks may either be straight or curved. The pistons are preferably double-acting pistons. A device includes at least one, and preferably a plurality of, such pneumatic stepper motor(s). The device may in particular be an MRI-compatible robotic system, more in particular for example an MRI-guided breast biopsy device.

A transmission, in particular a coaxial transmission or linear transmission, comprising a toothing, a tooth holder in which a plurality of tooth segments are accommodated to engage with the toothing, wherein the tooth segments are borne to be radially shiftable relative to the tooth holder, a drive element having a profiling for radially driving the tooth segments borne in a radially shiftable manner, wherein the transmission has inner initial stress.

A transmission, in particular a coaxial transmission or linear transmission, comprising a toothing, a tooth holder in which a plurality of tooth segments are accommodated to engage with the toothing, wherein the tooth segments are borne to be radially shiftable relative to the tooth holder, a drive element having a profiling for radially driving the tooth segments borne in a radially shiftable manner, wherein the transmission has inner initial stress.

A positioning unit includes two control carriages and a work carriage, it being possible to move the two control carriages and the work carriage on tracks that extend in parallel with one another. There is a working arm being articulated on a work base point on the work carriage and a control arm being articulated on a control base point on each of the control carriages. The control arms are articulated on the working arm at a control point of the working arm, the control point being spaced apart at a predefined lambda distance (d) from an end of the working arm that forms a working-point end and faces away from the work base point, and the two control base points and the work base point defining a triangle. At least two carriages of the two control carriages and the work carriage are movably arranged on a shared guide.

A positioning unit includes two control carriages and a work carriage, it being possible to move the two control carriages and the work carriage on tracks that extend in parallel with one another. There is a working arm being articulated on a work base point on the work carriage and a control arm being articulated on a control base point on each of the control carriages. The control arms are articulated on the working arm at a control point of the working arm, the control point being spaced apart at a predefined lambda distance (d) from an end of the working arm that forms a working-point end and faces away from the work base point, and the two control base points and the work base point defining a triangle. At least two carriages of the two control carriages and the work carriage are movably arranged on a shared guide.

In exemplary implementations, a target rod is actuated. The target rod is part of a set of threaded, elongated rods, the longitudinal axes of which are substantially parallel to each other. The set of rods has an interior region and a perimeter region. Actuators induce vibrations in a set of perimeter rods. These vibrations are substantially perpendicular to the longitudinal axes. Furthermore, the vibrations are transmitted to interior rods, causing a target rod in the interior region to rotate about, and translate along, the longitudinal axis of the target rod. The target rod undergoes stick-slip motion relative to adjacent rods.

In exemplary implementations, a target rod is actuated. The target rod is part of a set of threaded, elongated rods, the longitudinal axes of which are substantially parallel to each other. The set of rods has an interior region and a perimeter region. Actuators induce vibrations in a set of perimeter rods. These vibrations are substantially perpendicular to the longitudinal axes. Furthermore, the vibrations are transmitted to interior rods, causing a target rod in the interior region to rotate about, and translate along, the longitudinal axis of the target rod. The target rod undergoes stick-slip motion relative to adjacent rods.

A projectile including: a body having an internal space; and a mechanical stepper motor disposed in the body, the mechanical stepper motor including: a shuttle having one of a plurality of pockets and movable pins offset from each other with a first spacing; a body portion having the other of the plurality of pockets and movable pins offset from each other with a second spacing, where the first spacing is different from the second spacing; and actuation means for engaging at least one of the movable pins into a corresponding pocket to step one of the shuttle and body portion a predetermined linear and/or rotary displacement; wherein the mechanical stepper motor outputs the predetermined linear and/or rotary displacement to an actuated device operatively connected to the shuttle.

A projectile including: a body having an internal space; and a mechanical stepper motor disposed in the body, the mechanical stepper motor including: a shuttle having one of a plurality of pockets and movable pins offset from each other with a first spacing; a body portion having the other of the plurality of pockets and movable pins offset from each other with a second spacing, where the first spacing is different from the second spacing; and actuation means for engaging at least one of the movable pins into a corresponding pocket to step one of the shuttle and body portion a predetermined linear and/or rotary displacement; wherein the mechanical stepper motor outputs the predetermined linear and/or rotary displacement to an actuated device operatively connected to the shuttle.