concept generation

The Crane Tilt System focuses on simplicity by separating the 2 degrees of freedom, the pan and the tilt, into two independent mechanisms. The design consists of:

• A truss-like frame structure on which the components are mounted. 

• The head of the robot, which is on the top part of the frame and is only responsible for holding the facial monitor in place

This configuration was chosen because it minimizes the mass of the moving component; rotating only what is necessary. It is important to note that the axis of rotation for the monitor is in the middle of the monitor’s profile. The tablet’s tilt action is controlled by a pully with a motor and reel located on the base of the system. A servo motor will be used to rotate the reel, which will tilt the monitor via the pully system. The pan motion is operated via a totally separate mechanism. The base plate will be a large circle with teeth around the entirety of the inner surface. A platform will sit on top of an axis in the center of the circle via an axle and ball-bearings. A DC motor with a small gear attachment will mesh with the large static base and rotate the entire platform when the motor is engaged. The only concern with this design is that the pan mechanism has too much mobile mass.

The differential 3.0 concept directly iterates on the ARGOS 2.1 differential mechanism. The system operated with two rotating gears connected together. When both gears rotated simultaneously, the tablet panned. When the gears rotated opposite to each other, the system tilted. The main advantage to this design is that the mechanism itself was very compact, but heavy. The main drawback with the differential design was that it did little to reduce the weight of the system. The 2.1 design used pullies to control the differential via adjacent motors. This increased the weight and footprint of the design, making it difficult to manage. Additionally, the ARGOS 2.1 team reported that the longevity of the mechanism was poor. For the 3.0 design, the motors have been moved below the differential. The rotating gears in the differential will be controlled by shafts. This will minimize the footprint of the design, keeping all the weight in-line. One potential drawback to this design is that despite improving the weight distribution, it does little to reduce the amount of weight. Furthermore, an issue reported by the ARGOS 2.1 team was that tilting the head from the bottom produces a reverse-pendulum effect that makes the movement very jerky.  

The Wire-Gear system is focused on using two separate mechanisms for pan and tilt. It is based on the idea to not focus the weight in one central location and to minimize the contact with the design with the monitor. This is done with having the motor for tilt right behind the monitor to act as a counterweight for the monitor. The side view shows a motor, in its enclosure box shown as dash lines, being the back. The motor is in contact with a gear that has two wires connected to the top and bottom of the monitor secured by connectors to the monitor. Alongside this, the wires keep the monitor in its initial setting when not being used. This motor is the tilt motor and as it moves clockwise, the gears will then pull the top wire down, resulting in the monitor looking up. Counterclockwise results in a downward motion. s well the motor closure is connected to a secondary gear, stationary, that is in contact with a different gear connected with the monitor. These parts are meant to assist the wires in staying in contact with the monitor while also allowing movement.  Below the monitor and the enclosure box is a separate box focused on the electronic wiring, the Arduino board, and the pan motor. The pan motor is attached to a moveable gear that acts in rotating all aspects above it. This includes the enclosure, monitor, and its neck from which the top connects to the bottom. This results in a simple pan configuration and separates the locations of the motors for potential maintenance and disturbs the weight of the design rather than in one central location. This design is meant to ensure that center of mass remains in the same position throughout the change in movement.   

The Pulley System focuses on having the pan motor behind the monitor and having the tilt motor located below the tilt motor and monitor. Similar to the Wire-Gear system, this system separates the locations of the motors so that when the monitor is panning and or tilting, the center of mass remains in the same location. All motors in one enclosure while still evenly distributing the weight. The pan motor being behind the monitor reacts in a with pulley method as it relates to cable that is then connected to the monitor. It should be noted that the cable is connected at the center line of the monitor as to avoid cable movement being affected from the tilt movement. Otherwise, depending on the location of the pan motor and its cable, there would be tension or compression caused by tilt movement. The Tilt motor assists in keeping the monitor in a stationary position as it uses a spring for the cable. As well, this would limit the angle of the tilt to prevent any excessive tilt movement. Like the wire-gear system, it uses a cable attached to a connector to the top of the monitor although for this system, one cable is only needed to function.  

The piston tilt concept primarily focuses on simplicity. For the sake of simplicity, the tilt mechanism uses only 1 moving part with one actuator. For the pan mechanism, the concept uses the same base rotation mechanism used in the crane tilt concept. One main advantage to this design is that the control is very simple. The pan mechanism is also very simple, using a DC motor and a simple gear ratio. The largest drawback to this design is that piston actuation means that the tilt movement will likely be too fast and jerky. Smooth movement is one of the highest priorities for ARGOS 3.0, making this a larger drawback than it’s worth. 

The Quad Cable design utilizes four cables to determine the full rotation of the head.  Connected at the center by a ball joint, the design has a cable attached to the corners of the iPad to hold it up.  The motors are situated at the bottom of the torso and feed the cable through it to the head of the robot.  There is a monitor situated in the center of the torso which can be used by the pilot to display information to any viewers.  Important electronical systems are held at the bottom of the torso, such as the Arduino, control systems circuit and power bank. Wires are fed through the center on the central support to connect to the iPad and monitor.  The robot can interface with an external computer through the bottom of the torso.  This design will allow for accurate rotation of the head while also keeping most of the weight low.  The design also benefits from being supported to the base on a ball joint as it allows for a free range of movement while keeping the head supported.  Since design uses cables to control the movement, the mechanism will be more durable than other systems.  The design suffers from complexity regarding the system to move the cables as they must be under constant tension and bust work in unison to accurately move the head. Overall, the design allows for a durable robot with a desirable weight distribution that will provide accurate head movements if implemented correctly. 

The push rod design, similar to the Crane Tilt design, separates the two degrees of freedom and moves the actuators to a “waist” chassis which will house the electronics and interface with the MCBD. The pan angle (θp) is controlled by a central motor at the bottom of a long neck by a single stepper motor. The stepper motor was chosen for its precise, repeatable movement, its consistency key in accurate panning movement. The tilt angle (θt) is controlled by a prismatic joint, which will push a rod to tilt a lever by the display. This allows the tilt angle to be controlled by a simple Z coordinate of the prismatic joint, which if done correctly, can simplify the control system required to get accurate tilt movement, which would require no sensors in the “head” portion of the design. A key feature of all ARGOS 3.0 concepts is that the weight distribution of this design is much lower than ARGOS 2.1 which will allow for longer use before requiring maintenance. However, the potential standout feature of the Push Rod design, is the simplification of movement achieved by a stepper motor and linear actuator combination.