Compliant robot actuator mechanism.
A prismatic actuator for imparting a hopping motion to a supported load such as a leg of robot. The apparatus includes a direct drive motor, such as a voice coil, operable to provide translational motion. The apparatus includes a spring element and a prismatic guide assembly. The guide assembly is configured to support the direct drive motor to constrain the translational motion to be along a drive axis and support the spring element to constrain compression and expansion of the spring element along a longitudinal axis parallel to the drive axis. The apparatus includes a controller that: (1) first controls the direct drive motor to compress the spring element during a first time period beginning when the apparatus initially contacts a surface; and (2) second controls the direct drive motor to expand the spring element when the apparatus has zero velocity while contacting the surface.
BACKGROUND(1) 1. Field of the Description(2) The present description relates, in general, to prismatic actuators, and more particularly, to a prismatic parallel elastic mechanism for use in robot-environment interaction tasks, such as moving a support load such as a robot with a hopping motion (e.g., a translational elastic actuator used in a “hopping robot”).(3) 2. Relevant Background(4) Legged robots have been in wide use for many years and have many varying designs. For example, hopping robots are one type of design for legged robots or machines. Hopping robots are highly dynamic mobile platforms that have proven to be useful in many applications and environments. More recently, control and simulation of hopping robots has been simplified by representing these robots with reduced-dimensional models.(5) However, an ongoing challenge with the design of a hopping robot is that these robots require high speed and high force actuation due to the need to achieve non-trivial ground clearance to generate the hopping motion. In one exemplary design, a quadruped robot was constructed that could walk and also hop robustly using hydraulic actuators. Other designs have been proposed and researched that have achieved hopping motions with monopod, biped, and quadruped robots using electrical motors.(6) Untethered, hydraulically-actuated hopping robots can often outperform their electrical motor counterparts, but such hopping robots cause safety concerns for broader use outside the resear
1. An apparatus for producing relative motion between a supported load and its environment, comprising: a direct drive motor directly coupled to the supported load and the environment operable to provide translational motion between the support load and the environment; an elastic element directly coupled to the supported load and the environment; and a prismatic guide assembly first supporting the direct drive motor to constrain the translational motion and second supporting the elastic element to constrain compression and expansion of the elastic element to be parallel to the translational motion, wherein the direct drive motor comprises a translational voice coil motor, wherein the prismatic guide assembly comprises: a coil support supporting a coil element of the voice coil motor; a body support spaced apart from the coil support and supporting a body of the voice coil motor; and a translational bearing assembly constraining relative movement between the coil and body supports to be parallel to the drive axis, wherein the translational bearing assembly comprises first and second guide shafts extending between the coil support and the body support and positioned on opposite sides of the voice coil motor, wherein the elastic element comprises a compression spring coiled about exterior surfaces of one of the first and second guide shafts, and wherein the elastic element further comprises an additional compression spring coiled about exterior surfaces of another one of the first and second guide shafts.
8. An actuator mechanism, comprising: a voice coil comprising a coil and a body with an iron core and a space about the iron core for receiving the coil; a body support supporting the body of the voice coil; a coil support supporting the coil of the voice coil; a shaft extending between the coil support and body support; a translational bearing in the body support for slidingly engaging an end of the shaft; an elastic element coupled to the body and coil supports; and a controller first operating the voice coil to compress the elastic element during a first time period beginning when the actuator mechanism initially contacts a surface and second operating the voice coil to expand the elastic element during a second time period beginning when the actuator mechanism is sensed to have zero velocity while contacting the surface, wherein the first operating comprises applying a maximum voltage to the coil and wherein the second operating comprises applying a minimum voltage to the coil.
12. An apparatus for imparting a hopping motion to a supported load, comprising: a voice coil operable to provide translational motion; an elastic element; a prismatic guide assembly first supporting the voice coil to constrain the translational motion to be along a drive axis and second supporting the elastic element to constrain compression and expansion of the spring element along a longitudinal axis that is parallel to the drive axis of the voice coil; and a controller first controlling the voice coil to compress the elastic element during a first time period beginning when the apparatus is sensed to initially contact a surface and second controlling the voice coil to expand the elastic element during a second time period beginning when the apparatus is sensed to have zero velocity while contacting the surface, wherein the prismatic guide assembly comprises: a coil support supporting a coil element of the voice coil; a body support spaced apart from the coil support and supporting a body of the voice coil; and a bearing assembly constraining relative movement between the coil and body supports to be parallel to the drive axis, and wherein the bearing assembly comprises first and second guide shafts extending between the coil support and the body support and positioned on opposite sides of the voice coil.
15. An apparatus for producing relative motion between a supported load and its environment, comprising: a direct drive motor directly coupled to the supported load and the environment operable to provide translational motion between the support load and the environment; an elastic element directly coupled to the supported load and the environment; and a prismatic guide assembly first supporting the direct drive motor to constrain the translational motion and second supporting the elastic element to constrain compression and expansion of the elastic element to be parallel to the translational motion, wherein the direct drive motor comprises a translational voice coil motor, and wherein the direct drive motor includes a cooling element that actively cools the translational voice coil motor.