EXPRESSION

Block Screenshot

Contents

• Description
• Parameters
• Default properties
• Interfacing function
• Example

Description

The Expression block applies the specified Scilab expressions to its input.

Parameters

• number of inputs

  Block input can be a scalar or vector.

  Properties : Type 'vec' of size 1

• scilab expression

  The Scilab expression applied to the input.

  Properties : Type 'vec' of size 1

  All Scilab operators are supported.

  Only a restricted list of functions are supported in the expression.

  Name #rhs sin 1 cos 1 tan 1 asin 1 acos 1 atan 1 atan2 2

  Name #rhs sinh 1 cosh 1 tanh 1 asinh 1 acosh 1 atanh 1

  Name #rhs exp 1 log 1 log10 1 int 1 round 1 ceil 1 floor 1

  Name #rhs sign 1 abs 1 min 2 max 2

  In the provided expression, any subexpression being an exponent more than 1-character long must end with a space, to be correctly displayed on the block's icon. This constrain has no consequence on the computational validity of the expression. Examples: "u1^12-u2", "u1^ 12-u2", "u1^abc - 3", "u1^(u2-3) + 4" will be correctly displayed, while "u1^abc-3" would be displayed as "u1^{abc-3}" (but well computed as u1^abc + 3) and "u1^(u2-3)+4" as "u1^{(u2-3)+4}" instead of "u1^{(u2-3)} + 4". "u1^abc - 3" and "u1^(u2-3) + 4" will have to be entered instead.

• use zero-crossing

  Select to enable zero crossing detection.

  Properties : Type 'vec' of size 1

Default properties

• always active: no

• direct-feedthrough: yes

• zero-crossing: yes

• mode: yes

• regular inputs:

  - port 1 : size [1,1] / type 1

  - port 2 : size [1,1] / type 1

• regular outputs:

  - port 1 : size [1,1] / type 1

• number/sizes of activation inputs: 0

• number/sizes of activation outputs: 0

• continuous-time state: no

• discrete-time state: no

• object discrete-time state: no

• name of computational function: evaluate_expr

Example

The following example calculate an arbitrary expression with multiple different configuration or blocks.

y = u(1) - u(2) - u(3)

Interfacing function

• SCI/modules/scicos_blocks/macros/Misc/EXPRESSION.sci