Traction control device and traction control method
A parameter calculation part calculates an adaptive gain coefficient ‘k’ for the road surface conditions, based on frictional coefficient μ and a slip ratio λ from an acquisition part and a coefficient ‘b’ in a storage part. Subsequently, the parameter calculation part calculates an adaptive time constant τ by which the stability of traction control can be ensured, based on the gain coefficient ‘k’ and a coefficient ‘a’ within the storage part. Along with the calculated gain coefficient ‘k’ being set in a gain multiplication part, the calculated time constant τ is set in a filter part. According to these settings, model following control is executed by taking, as a reference model, an adhesion model in which the driving wheel does not slip. This enhances slip prevention performance while ensuring control stability, making stable travel possible while ensuring the required drive force in accordance with road surface state.
1. A traction control device that performs traction control for a moving body having a driving wheel which is driven by a motor, comprising:
an acquisition part configured to acquire a torque instruction value for said driving wheel, the rotational speed of said driving wheel, and friction coefficient information for the road surface upon which said driving wheel runs;
a torque command value calculation part configured to calculate the torque command value to be outputted to the motor for driving said driving wheel, on the basis of said acquired torque instruction value and a correction amount;
an estimated torque value calculation part configured to calculate an estimated value of torque operating upon said driving wheel, on the basis of said calculated torque command value and a model for torque transmission to said driving wheel;
an inverse torque value calculation part configured to calculate a torque value corresponding to said acquired rotational speed, according to a reference model in which no slip of said driving wheel takes place;
a filter part configured to apply a first-order delay to the difference between the result of calculation by said estimated torque value calculation part and the result of calculation by said inverse torque value calculation part; and
a gain multiplication part configured to feed back, to said torque command value calculation part, as said correction amount, the result obtained by multiplying said difference to which said first-order delay has been applied by a gain coefficient; wherein
said gain coefficient takes a value which is adaptively set by using said acquired friction coefficient information; and
the time constant of said filter part takes a value which is adaptively set by utilizing said acquired friction coefficient information, or a value which is determined on the basis of the estimated value of the maximum value taken by said gain coefficient.
2. A traction control device according to claim 1 , wherein
a dead time and a motor torque response time are included in said torque transfer model; and
said traction control device further comprises a time constant setting part configured to set said time constant to a value that, while corresponding to said gain coefficient, is effective for ensuring width of the control band, depending on said dead time, said motor torque response time period, the weight of said moving body, and the moment of inertia and the radius of said driving wheel.
3. A traction control device according to claim 2 , wherein said time constant setting part calculates said time constant τ from said gain coefficient ‘k’ according to Equation (I) below, on the basis of a constant ‘a’ that is determined in advance to correspond to said dead time, said motor torque response time period, the weight of said moving body, and the moment of inertia and the radius of said driving wheel
τ≧ a·k (I).
4. A traction control device according to claim 3 , further comprising a gain coefficient setting part configured to set said gain coefficient by utilizing said acquired friction coefficient information, according to the weight of said moving body and the moment of inertia and the radius of said driving wheel.
5. A traction control device according to claim 2 , further comprising a gain coefficient setting part configured to set said gain coefficient by utilizing said acquired friction coefficient information, according to the weight of said moving body and the moment of inertia and the radius of said driving wheel.
6. A traction control device according to claim 1 , further comprising a gain coefficient setting part configured to set said gain coefficient by utilizing said acquired friction coefficient information, according to the weight of said moving body and the moment of inertia and the radius of said driving wheel.
7. A traction control device according to claim 6 , wherein:
said acquisition part further acquires slip ratio information for said driving wheel; and
said gain coefficient setting part calculates said gain coefficient ‘k’ according to Equation (II) below, on the basis of a constant ‘d’ that is determined in advance to correspond to the weight of said moving body and the moment of inertia and the radius of said driving wheel, a constant ‘e’ that is determined in advance, a friction coefficient μ corresponding to said friction coefficient information that has been acquired, and a slip ratio λ corresponding to said slip ratio information that has been acquired
k=d/μ+e·λ (II).
8. A traction control device according to claim 6 , wherein
said acquisition part further acquires slip ratio information for said driving wheel; and
said gain coefficient setting part calculates said gain coefficient ‘k’ according to Equation (III) below, on the basis of a constant ‘b’ that is determined in advance to correspond to the weight of said moving body and the moment of inertia and the radius of said driving wheel, a constant ‘c’ that is determined in advance, a friction coefficient μ corresponding to said friction coefficient information that has been acquired, and a slip ratio λ corresponding to said slip ratio information that has been acquired
k=b ·(λ/μ)+ c (III).
9. A traction control device that performs traction control for a moving body having a driving wheel which is driven by a motor, comprising:
an acquisition part configured to acquire a torque instruction value for said driving wheel, the rotational speed of said driving wheel, friction coefficient information for the road surface upon which said driving wheel runs, and an actual torque value that drives said motor;
a torque command value calculation part configured to calculate the torque command value to be outputted to the motor for driving said driving wheel, on the basis of said acquired torque instruction value and a correction amount;
an inverse torque value calculation part configured to calculate a torque value corresponding to said acquired rotational speed, according to a reference model in which no slip of said driving wheel takes place;
a filter part configured to apply a first-order delay to the difference between said acquired actual torque part and the result of calculation by said inverse torque value calculation part; and
a gain multiplication part configured to feed back to said torque command value calculation part, as said correction amount, the result obtained by multiplying the value to which said first-order delay has been applied by a gain coefficient; and wherein
said gain coefficient takes a value which is adaptively set by using said acquired friction coefficient information; and
the time constant of said filter part takes a value which is adaptively set by utilizing said acquired friction coefficient information, or a value which is determined on the basis of the estimated value of the maximum value taken by said gain coefficient.
10. A traction control method that performs traction control for a moving body having a driving wheel which is driven by a motor, comprising the steps of:
an acquisition step of acquiring a torque instruction value for said driving wheel, the rotational speed of said driving wheel, and friction coefficient information for the road surface upon which said driving wheel runs;
a torque command value calculation step of, on the basis of said acquired torque instruction value and a correction amount at the present time point, calculating a torque command value to be outputted to the motor for driving said driving wheel;
an estimated torque value calculation step of, on the basis of said calculated torque command value and a model for torque transmission to said driving wheel, calculating an estimated value of torque operating upon said driving wheel;
an inverse torque value calculation step of calculating a torque value corresponding to said acquired rotational speed, according to a reference model in which no slip of said driving wheel takes place;
a first-order delay application process of applying a first-order delay to the difference between the result of calculation in said estimated torque value calculation step and the result of calculation in said inverse torque value calculation step with a time constant which has either a value which is adaptively set by utilizing said acquired friction coefficient information, or a value which is determined on the basis of the estimated value of the maximum value taken by said gain coefficient which is adaptively set by utilizing said acquired friction coefficient information; and
a correction amount updating step of taking the result obtained by multiplying said difference to which said first-order delay has been applied by said gain coefficient, as a new correction amount; and wherein
said acquisition step, said torque command value calculation step of taking said new correction amount as the correction amount at said present time point, said estimated torque value calculation step, said inverse torque value calculation step, said first-order delay application step, and said correction amount updating step are repeated.
11. A non-transitory computer readable recording medium, having recorded thereon a traction control program that, when executed, causes a calculation part to execute a traction control method comprising:
an acquisition step of acquiring a torque instruction value for said driving wheel, the rotational speed of said driving wheel, and friction coefficient information for the road surface upon which said driving wheel runs;
a torque command value calculation step of, on the basis of said acquired torque instruction value and a correction amount at the present time point, calculating a torque command value to be outputted to the motor for driving said driving wheel;
an estimated torque value calculation step of, on the basis of said calculated torque command value and a model for torque transmission to said driving wheel, calculating an estimated value of torque operating upon said driving wheel;
an inverse torque value calculation step of calculating a torque value corresponding to said acquired rotational speed, according to a reference model in which no slip of said driving wheel takes place;
a first-order delay application process of applying a first-order delay to the difference between the result of calculation in said estimated torque value calculation step and the result of calculation in said inverse torque value calculation step with a time constant which has either a value which is adaptively set by utilizing said acquired friction coefficient information, or a value which is determined on the basis of the estimated value of the maximum value taken by said gain coefficient which is adaptively set by utilizing said acquired friction coefficient information; and
a correction amount updating step of taking the result obtained by multiplying said difference to which said first-order delay has been applied by said gain coefficient, as a new correction amount; and wherein
said acquisition step, said torque command value calculation step of taking said new correction amount as the correction amount at said present time point, said estimated torque value calculation step, said inverse torque value calculation step, said first-order delay application step, and said correction amount updating step are repeated.