Control of interconnected trolleys

A hoist trolley assembly that comprises a first hoist trolley, drive equipment for the first hoist trolley, a second hoist trolley, drive equipment for the second hoist trolley, and a control system, the first hoist trolley being connected to the second hoist trolley in such a manner that the first hoist trolley and the second hoist trolley are arranged to move at the same speed, both the drive equipment of the first hoist trolley and the drive equipment of the second hoist trolley comprising an electric motor, the control system being adapted to receive a preliminary speed reference for the interconnected first hoist trolley and second hoist trolley and to form a final speed reference for the first hoist trolley by using initial data that comprise the preliminary speed reference, wherein the control system is adapted to use in forming the final speed reference for the first hoist trolley a hoist trolley coefficient krb that is obtainable by an equation

• k
• rb
• =
• T
• A_nom
• T
• B_nom
• ·
• v
• B_nom
• v
• A_nom
• ·
• m
• TB
• +
• m
• LB
• m
• TA
• +
• m
• LA
• ,
• wherein
• TA—nom=the rated torque of the electric motor of the first hoist trolley
• TB—nom=the rated torque of the electric motor of the second hoist trolley
• vA—nom=nominal speed of the first hoist trolley
• vB—nom=nominal speed of the second hoist trolley
• mTA=dead weight of the first hoist trolley
• mTB=dead weight of the second hoist trolley
• mLA=load of the first hoist trolley
• mLB=load of the second hoist trolley,
• and the control system comprises a programmable logic controller and a first restriction block, the programmable logic controller being adapted to form a preliminary speed reference nrefA for the first hoist trolley, the preliminary speed reference being obtainable by an equation
• n
• refA
• =
• min
• ⁡
• (
• v
• A
• ,
• v
• B
• )
• v
• A
• ·
• n
• ref
• ,
• the first restriction block being adapted to form a restricted speed reference nrampA for the first hoist trolley by restricting the first time derivative of the preliminary speed reference nrefA of the first hoist trolley at its maximum to an acceleration value arampA of the first restriction block.