Passive manipulators have no actuators, or in other words, there is no motor or pneumatic cylinder which is directly attached to the manipulator. The rules of many robotics games include limitations on the number of motors and/or the amount of pneumatic air storage a robot can possess. Designing a passive manipulator allows the robot’s actuators to be used for additional functions. Passive manipulators are moved by being attached to a drivetrain or another active manipulator. They can also contain stored energy from rubber bands or latex tubing. Passive manipulators can be some of the easiest and quickest types of manipulators to assemble, although they can be very complex with manual releases and re-set mechanisms. Some examples of passive manipulators which can be used to play a robotics game include:
Plows are perhaps the simplest and quickest to design of all the manipulators. Plows are usually attached to the drivetrain and typically their functions are pushing game pieces around and/or keeping the robot from driving up on game pieces and becoming immobile.
Some parts which can be used to assemble plows include structural metal and Polycarbonate Sheeting. Standoffs are often also used to extend out from a plow to help direct game pieces.
Forks and Scoops (types of passive claws)
Forks and scoops are typically attached to an arm and are usually designed to slide under game pieces in order to pick them up. Forks and scoops can be quick and easy to assemble. Although they can be complex, such as an assembly which can be inserted into a Ring game piece and has a manual pick-up and release mechanism, or a custom Polycarbonate Sheet which is shaped to pick up and release a Cone game piece.
Structural metal, Polycarbonate Sheet, and Standoffs are commonly used to assemble forks and scoops.
|Sample Scoop using Plates||Sample Scoop using Standoffs|
|Sample Game Piece Shield|
Often games will have a rule limiting the number of game pieces a robot can possess. In this case, if a game piece falls onto the robot it can limit its play. Even if there is not a possession rule, if a game piece falls onto the robot and under an arm, it can be a problem. Shields are designed to keep game pieces off of the robot.
There are many options for parts/materials which can be used to assemble a shield for a robot. Some rigid options include metal Bar, metal Plate, and Polycarbonate Sheet. Some flexible options include rubber bands, latex tubing, zip ties, Anti-Slip Mat, VELCRO® brand ONE-WRAP® and the VEX Robotics Competition rules currently allows 1/8” (or local metric equivalent) braided nylon rope.
Some robot games have an entanglement rule. If this is the case, additional thought should be used when designing a shield which uses flexible material.
Game Piece Slides
|Sample Game Piece Slide|
Game piece slides are usually combined with an active manipulator such as a roller claw, roller intake, or conveyer belt. Typically, an active intake pushes game pieces up the slide. Then the game pieces are scored into a goal by the intake reversing its direction, or it swings out of the way and the game pieces slide out.
Structural metal and a Polycarbonate Sheet are commonly used to assemble game piece slides.
The combination of an active manipulator and slide may require more time and planning than the passive manipulators which have been previously discussed.
Many robotics games have a maximum size (length, width, and height) the robot may have at the start of a match, but then will allow the robot to expand after the match begins. These expansion zones can be used with drivetrains, which in the extreme case, are sometimes referred to as WallBots. Drivetrain expansion zones can be as simple as a second set of wheels swinging down and locking into place expanding the robot’s footprint and keeping it from falling over when lifting objects.
|Sample Expansion Zone|
Expanding zones in drivetrains can use an omni-directional drive to expand the chassis by one side of the drive moving sideways in the opposite direction from the other side.
Expansion zones can also be used in manipulators such as claws, arms, lifts, game piece slides, plows, etc. Passive expansion zones often contain stored energy from stretched rubber bands or latex tubing or use potential energy from gravity. These expansion zones can either flip out using a hinge point or expand linearly using a scissor assembly or using Acetal Slide Trucks and Linear Slide Tracks from the Linear Motion Kit.
Expansion zones can sometimes require a trigger and/or a locking mechanism. Triggers can be designed from things like a short zip tie placed in the hole of structural metal. The zip tie is pulled out when an arm lifts, releasing the assembly. Locking mechanisms can be designed from things like, shafts or screws which falls/slides into a structural metal hole, a notch cut into a piece of metal bar which catches onto a screw/shaft, or the Winch Pawl and Winch Racket Gear from the Winch and Pulley Kit.
Expansion Zones will most likely require extended time and planning to assemble successfully.