An actuator assembly comprises a static part and a movable part. A helical bearing arrangement supporting the movable part on the static part guides helical movement of the movable part with respect to the static part around a helical axis. One or more actuators, that are not shape memory alloy actuators, are arranged to drive movement of the movable part around the helical axis, which thereby includes a component of translational movement along the helical axis. The helical movement increases the force within the actuator assembly allowing actuation of heavier movable parts, and may improve posture.

A ball spline device includes a spline shaft, the outer side wall provided with raceway grooves extending in the axial direction, each raceway groove comprising, a first groove section and a second groove section, and the width of the second groove section being greater than that of the first groove section; a spline nut coaxially fitted over the spline shaft; and first rolling bodies. When the spline nut is located at a first position, the first rolling bodies are located in the first groove sections and in constraint fit with the first groove sections; and when the spline nut is located at a second position, the first rolling bodies are located in the second groove sections, such that the spline nut and the spline shaft have a preset movement amount in the circumferential direction. Further provided are an automated guided vehicle and a stereoscopic warehouse system.

A ball spline device includes a spline shaft, the outer side wall provided with raceway grooves extending in the axial direction, each raceway groove comprising, a first groove section and a second groove section, and the width of the second groove section being greater than that of the first groove section; a spline nut coaxially fitted over the spline shaft; and first rolling bodies. When the spline nut is located at a first position, the first rolling bodies are located in the first groove sections and in constraint fit with the first groove sections; and when the spline nut is located at a second position, the first rolling bodies are located in the second groove sections, such that the spline nut and the spline shaft have a preset movement amount in the circumferential direction. Further provided are an automated guided vehicle and a stereoscopic warehouse system.