Energy efficient motion control system
First Claim
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1. A method for generating a control signal for controlling an operation of a motion control system suitable for positioning a load, comprising the steps of:
- determining a cost function based on a model of energy consumption of the system and a function of a tracking time, determining the model according to
P(x,u)=Ru2+Ktux2,wherein P(x, u) is the energy consumption of the system, x is a state of the motor, u is a control input to the motor, R is a resistance of windings of the motor, x2 is a second component of the state of the motor x representing an angular velocity of the motor, and Kt is a torque constant of the motor;
minimizing the cost function subject to constraints to determine a trajectory of the control signal; and
generating the control signal based on the trajectory and a current state of the system, wherein the steps of the method are performed by a processor.
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Abstract
A control signal for controlling an operation of a motion control system suitable for positioning a load is generated using determining a cost function based on a model of energy consumption of the system and a function of a tracking time; and minimizing the cost function subject to constraints to determine a trajectory of the control signal. The control signal is generated based on the trajectory and a current state of the system, wherein the steps of the method are performed by a processor.
9 Citations
16 Claims
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1. A method for generating a control signal for controlling an operation of a motion control system suitable for positioning a load, comprising the steps of:
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determining a cost function based on a model of energy consumption of the system and a function of a tracking time, determining the model according to
P(x,u)=Ru2+Ktux2,wherein P(x, u) is the energy consumption of the system, x is a state of the motor, u is a control input to the motor, R is a resistance of windings of the motor, x2 is a second component of the state of the motor x representing an angular velocity of the motor, and Kt is a torque constant of the motor; minimizing the cost function subject to constraints to determine a trajectory of the control signal; and generating the control signal based on the trajectory and a current state of the system, wherein the steps of the method are performed by a processor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
wherein P(x, u) is the energy consumption of the system, x is a state of the motor, u is a control input to the motor, R is a resistance of windings of the motor, x2 is a second component of the state of the motor x representing an angular velocity of the motor, Ke is a constant coefficient of an eddy current of the motor, Kh is a constant coefficient of hysteresis losses in the motor, Ks is a constant coefficient of the switching loss at an amplifier, γ
is the Steinmetz constant, and Kt is a torque constant of the motor.
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5. The method of claim 4, further comprising:
determining the model according to
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6. The method of claim 5, further comprising:
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determining the cost function according to
E=∫
0TQ(x(t),u(t))dtwherein T is the tracking time.
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7. The method of claim 5, further comprising:
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determining the cost function according to
E=∫
0tf (ε
+Q(x(t),u(t)))dt,wherein tf is an unspecified tracking time, and ε
is a preference constant.
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8. The method of claim 1, wherein the constraints includes one or combination of an acceleration constraint of a motor, a velocity constraint of the motor, an input current constraint of the motor, a dynamic constraint of the motor, the tracking time, an initial state of the motor, and a final state of the motor.
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9. The method of claim 1, further comprising:
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determining a Hamiltonian based on the cost function and the constraints; determining a set of conditions minimizing the Hamiltonian; and determining the trajectory that satisfies the set of conditions.
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10. The method of claim 9, further comprising:
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formulating a resultant multi-point boundary value problem based on the set of conditions; and solving the problem to produce the trajectory.
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11. The method of claim 9, wherein the minimizing comprises:
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defining a Hamiltonian based on the cost function and the constraints, wherein the Hamiltonian includes a first Hamiltonian for a positive control signal and a positive energy consumption, a second Hamiltonian for a negative control signal and the positive energy consumption, and a third Hamiltonian for the negative control signal and the negative energy consumption; determining a first sot of conditions for a first sub-trajectory, such that the first Hamiltonian is minimized; determining a second set of conditions for a second sub-trajectory, such that the second Hamiltonian is minimized; determining a third set of conditions for a third sub-trajectory, such that the third Hamiltonian is minimized; and determining the set of conditions based on the first, the second, and the third set of conditions.
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12. The method of claim 11, further comprising:
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determining nonlinear algebraic equations (NAE) satisfying the set of conditions, such that the NAE defines the control signal at a current point of the tracking time; determining boundary conditions, wherein the boundary conditions include terminal conditions, and entry conditions for each of the first, the second, and the third sub-trajectory; determining nonlinear ordinary differential equations (ODE) satisfying the boundary conditions, such that the ODE defines a state and a costate of the system at the current point of the tracking time; and solving the ODE and the NAE alternately over the tracking time until the boundary conditions are satisfied to produce the trajectory.
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13. The method of claim 12, wherein the NAE includes linear algebraic equations.
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14. The method of claim 1, further comprising:
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determining a preliminary trajectory; and selecting the preliminary trajectory as the trajectory, if a gradient of the cost function with respect to the preliminary trajectory is less than a threshold.
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15. The method of claim 14, further comprising:
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determining a finite dimensional optimization problem that minimizes the cost function subject to the constraint; and determining the trajectory by solving the problem.
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16. The method of claim 15, further comprising:
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performing a discretization of decision variables, the cost function, and the constraints; approximating an infinite dimensional optimization problem with the finite dimensional optimization problem; generating a preliminary trajectory; determining a gradient of the cost function with respect to the preliminary trajectory; determining the trajectory based on the preliminary trajectory, if the gradient is less than a threshold; and
otherwise;updating the preliminary trajectory based on the gradient and the constraints; and repeating the determining the gradient and the determining the trajectory.
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Specification