Method and apparatus for measuring mass based on torque equilibrium

A method of using an apparatus for measuring mass based on torque equilibrium, the apparatus comprising:

• a main blade for supporting and balancing a lever and parts arranged on the lever;
• a displacement measuring device for measuring a position of the lever;
• an electromagnetic torquer for balancing the apparatus after a balance weight is coarsely loaded during measuring;
• a product tooling on which a product to be measured is arranged and fixedly connected;
• wherein the product tooling is fixed on a slider which freely slides along a guide rail;
• a locking block is provided to fixedly lock the product after the product slides in place;
• the guide rail is fixed on the lever;
• a laser displacement sensor is provided to measure a displacement of the product along the guide rail;
• a lifting mechanism is provided to lift the lever and the parts arranged on the lever to separate from the main blade;
• a load cell is provided above the lifting mechanism and is configured to measure mass and center of mass of the product, such that the balance weight with an appropriate mass is loaded by an automatic loading system;
• and a minor blade is provided to provide an accurate loading point for the balance weight;
• the method comprising:
• 1) mounting the product tooling on the slider;
• 2) lowering the lifting mechanism and balancing the product tooling using the balance weight and the electromagnetic torquer, wherein a balancing load is represented by m1and the balanced product tooling is at an initial position;
• 3) moving the product tooling along the guide rail for a distance;
• locking the product tooling by the locking block;
• measuring the distance to obtain a displacement distance L1;
• and balancing the product tooling, wherein a balancing load is represented by m2;
• 4) calculating the mass of the product tooling according to
• M
• t
• =
• (
• m
• 2
• -
• m
• 1
• )
• ·
• L
• L
• 1
• ,
• wherein L represents the horizontal distance between blade marks of the main blade and minor blade, and the Mt represents the mass of the product tooling;
• 5) starting the lifting mechanism to lift the lever;
• restoring the product tooling to the initial position;
• fixing the product on the product tooling;
• and coarsely measuring mass of the product to obtain a coarsely measured mass M′;
• 6) lowering the lifting mechanism and balancing the product tooling, wherein a balancing load is represented by m3;
• 7) moving the product tooling along the guide rail at a distance;
• locking the product tooling by the locking block;
• measuring the distance to obtain a displacement distance L2;
• 8) coarsely loading the balance weight until the apparatus is within a controllable range of the electromagnetic torquer, wherein a balancing load is represented by m4;
• 9) calculating the sum of the mass of the product tooling and the product according to
• M
• +
• M
• t
• =
• (
• m
• 3
• -
• m
• 4
• )
• ·
• L
• L
• 2
• ,
• wherein mass of the product is M;
• and
• 10) calculating the mass of the product according to
• M
• =
• (
• m
• 3
• -
• m
• 4
• )
• ·
• L
• L
• 2
• -
• (
• m
• 2
• -
• m
• 1
• )
• ·
• L
• L
• 1
• .