Belt-Cable End

Tip of the cord of a pulley system

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Libraries:
Simscape / Multibody / Belts and Cables

Description

The Belt-Cable End block represents the tip of a cord by which to anchor, drive, or load a pulley system. This tip serves as an interface between the belt-cable domain specific to pulleys and the frame domain general to all multibody components. A belt-cable port (E) identifies the cord whose tip this block defines and its relative placement within a pulley system. A frame port (R) identifies the local reference frame of the tip and its placement in the broader multibody model.

The cord is inextensible. Its effective length can change only if a source of a cord is provided—for example, in the form of a spool. If the second terminus of the cord is another tip, the length of the cord is fixed, and so must be the distance around the pulleys from one tip to the other. This distance is monitored during simulation, through calculations based on the placement and geometry of the pulleys. The two measures—the length and the distance—must always agree.

The cord is also always taut. From one of its tips to the nearest pulley, the cord must form a straight line, one tangent to the circumference of the pulley and parallel to its plane of rotation. The reference frame of the tip is placed on this line with its z-axis directed along it and away from the pulley. Constraints imposed on the tip by components outside of the pulley system must act without interfering with this alignment.

Note that the frame and belt-cable ports belong to different physical domains. As a rule, ports connect only to like ports—frame ports to other frame ports, belt-cable ports to other belt-cable ports. The belt-cable domain imposes also the special requirement that each network of belt-cable connection lines contain one (and no more than one) Belt-Cable Properties block. The necessary attributes of the pulley cord are specified through this block.

Examples

Block and Tackle with Four Pulleys

Models a block and tackle with four pulleys. Torque is applied to a winch which acts through the pulley mechanism to lift a load. Blocks from the Simscape™ Multibody™ Belts and Cables library are used to model the block and tackle.

• Open Model

Cable-Driven Cross Slide Table

Models an XY cross positioning table that uses a cable-driven mechanism. A single cable wraps around seven different pulleys and converts the rotational angle of the two input pulleys to the x-y position of the table.

• Open Model

Cable Robot

Models a cable robot. The robot comprises 8 independent belt-cable circuits which control the 6 degrees-of-freedom of the mover. A ball is dropped from a fixed height down the center axis of the mechanism. The mover initially starts directly below the ball and the contact is modeled between the mover and the ball such that the ball bounces elastically when striking the mover. The objective of the mover is to perform increasingly complex maneuvers between successive bounces of the ball. The mover is motion actuated from which the necessary cable, pulley, and motor spool kinematics are computed.

• Open Model

Pulley Mechanism Right Angle Drive

Models a pulley mechanism that takes a torque applied to a winch and transmits it to a pulley rotated at 90 degrees to that winch. This example uses blocks from the Simscape Multibody Belts and Cables library to model a pulley mechanism that is not all in a single plane.

• Open Model

Cable Driven Space Manipulator

Models a cable driven space manipulator. The manipulator comprises of 2 links connected via a system of revolute joints. Each link consists of belt-cable circuits which drive the movements of the manipulator. It also consists of a spring-damper system which provides different stiffness requirements. A space application is shown in this example where the objective of the manipulators is to capture a small satellite. The manipulators start from folded states and then perform necessary maneuvers to extend and reach the desired position. The pulleys are motion actuated from which necessary belt-cable kinematics are computed.

• Open Model

Tower Crane with Trolley and Hoist

Models a tower crane with a trolley and a hoist. The hoist can raise and lower a load, and the trolley moves the load towards and away from the tower. Blocks from the belts and cables library are used to model the pulleys that control lifting the load and moving the trolley.

• Open Model

Elevator

Models an elevator system in Simscape™ Multibody™. The system is comprised of belt-cable pulley circuits which control the movement of the elevator and the door mechanism. The cable is approximated to be extensible by using high stiffness springs between the belt cable ends and the elevator. The motor pulley is motion actuated based on the necessary elevator kinematics computed from the Floor Number inputs. Effects of people entering and leaving the elevator are modeled using general variable mass blocks.

• Open Model

Forklift

Models a forklift which uses the hydraulic and pulley mechanisms to perform the lift action. The tilting of masts is also controlled by hydraulic cylinders. The forklift comprises of 3 masts, namely main mast, top mast and fork mast. The main mast is connected to the chassis by revolute joints and its tilting is governed by the hydraulic tilt cylinders. The top mast slides over the main mast and its motion is governed by the hydraulic lift cylinders. The fork mast slides on the top mast and hangs through belt-cable circuits which drives the movement of the fork mast. A common warehouse application is shown in this example where the objective of the forklift is to grab a box, pass over a bump and place the box in the racks. Spatial Contact Force blocks are used at all contact locations to model the contact between the bodies. The contact between the ground surface and the wheels are modeled using infinite plane block and the contact between the forks and the box are modeled using the point blocks.

• Open Model

Ports

Frame

R — Local reference frame

frame

Reference frame by which to connect the tip of the cord to the remainder of a multibody model.

Belt-Cable

E — Cord attachment point

belt-cable

Point at which to terminate the cord of a pulley system.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018a